arm64: IOMMU-backed DMA mapping

Taking inspiration from the existing arch/arm code, break out some generic functions to interface the DMA-API to the IOMMU-API. This will do the bulk of the heavy lifting for IOMMU-backed dma-mapping.

Whilst this RFC series is aimed at enabling arm64, once any remaining obvious issues in the common code are addressed we can complete the refactoring by porting arch/arm over for a merge-worthy series.

Signed-off-by Robin Murphy <[email protected]>

---
 drivers/iommu/Kconfig     |   7 +
 drivers/iommu/Makefile    |   1 +
 drivers/iommu/dma-iommu.c | 552 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/dma-iommu.h |  94 ++++++++
 4 files changed, 654 insertions(+)
 create mode 100644 drivers/iommu/dma-iommu.c
 create mode 100644 include/linux/dma-iommu.h

drivers/iommu/Kconfig +0 -0

index a839ca9..19027bb 100644

drivers/iommu/Kconfig +4 -0

+       depends on NEED_SG_DMA_LENGTH
+       select IOMMU_API
+       select IOMMU_IOVA
+
 config FSL_PAMU
        bool "Freescale IOMMU support"
        depends on PPC_E500MC

drivers/iommu/Makefile +1 -0

index 0b1b94e..37bfc4e 100644
@@ -1,6 +1,7 @@
 obj-$(CONFIG_IOMMU_API) += iommu.o
 obj-$(CONFIG_IOMMU_API) += iommu-traces.o
 obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
+obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
 obj-$(CONFIG_IOMMU_IOVA) += iova.o
 obj-$(CONFIG_OF_IOMMU) += of_iommu.o
 obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o msm_iommu_dev.o

drivers/iommu/dma-iommu.c new file +31 -0

new file mode 100644
index 0000000..b97cc0b9
@@ -0,0 +1,552 @@
+/*
+ * A fairly generic DMA-API to IOMMU-API glue layer.
+ *
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * based in part on arch/arm/mm/dma-mapping.c:
+ * Copyright (C) 2000-2004 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define pr_fmt(fmt)    "%s: " fmt, __func__
+
+#include <linux/dma-contiguous.h>
+#include <linux/dma-iommu.h>
+#include <linux/iova.h>
+
+int iommu_dma_init(void)
+{
+       return iommu_iova_cache_init();
+}

drivers/iommu/dma-iommu.c new file +8 -0

+       return addr - ((dma_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
+}
+
+static int __dma_direction_to_prot(enum dma_data_direction dir, bool coherent)
+{
+       int prot = coherent ? IOMMU_CACHE : 0;
+
+       switch (dir) {

drivers/iommu/dma-iommu.c new file +5 -0

+       /* Alignment should probably come from a domain/device attribute... */
+       return alloc_iova(iovad, length, limit_pfn, false);
+}
+
+/*

drivers/iommu/dma-iommu.c new file +13 -0

+       dma_addr_t addr_lo, addr_hi;
+       int i, prot = __dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent);
+
+       iova = __alloc_iova(dev, size, coherent);
+       if (!iova)
+               return DMA_ERROR_CODE;
+
+       addr_hi = addr_lo = iova_dma_addr(iovad, iova);
+       for (i = 0; i < count; ) {
+               unsigned int next_pfn = page_to_pfn(pages[i]) + 1;
+               phys_addr_t phys = page_to_phys(pages[i]);
+               unsigned int len, j;
+

drivers/iommu/dma-iommu.c new file +36 -0

+       return dev_dma_addr(dev, addr_lo);
+fail:
+       iommu_unmap(domain, addr_lo, addr_hi - addr_lo);
+       __free_iova(iovad, iova);
+       return DMA_ERROR_CODE;
+}
+
+int iommu_dma_release_iova_mapping(struct device *dev, dma_addr_t iova,
+               size_t size)
+{
+       struct iommu_dma_domain *dom = get_dma_domain(dev);
+       struct iova_domain *iovad = dom->iovad;
+       size_t offset = iova_offset(iovad, iova);
+       size_t len = iova_align(iovad, size + offset);
+
+       iommu_unmap(dom->domain, iova - offset, len);
+       free_iova(iovad, iova_pfn(iovad, iova));
+       return 0;
+}
+
+struct page **iommu_dma_alloc_buffer(struct device *dev, size_t size,
+               gfp_t gfp, struct dma_attrs *attrs,
+               void (clear_buffer)(struct page *page, size_t size))
+{
+       struct page **pages;
+       int count = size >> PAGE_SHIFT;
+       int array_size = count * sizeof(struct page *);
+       int i = 0;
+
+       if (array_size <= PAGE_SIZE)
+               pages = kzalloc(array_size, GFP_KERNEL);
+       else
+               pages = vzalloc(array_size);
+       if (!pages)
+               return NULL;
+

drivers/iommu/dma-iommu.c new file +14 -0

+       dom = kzalloc(sizeof(*dom), GFP_KERNEL);
+       if (!dom)
+               return NULL;
+
+       /*
+        * HACK: We'd like to ask the relevant IOMMU in ops for a suitable
+        * domain, but until that happens, bypass the bus nonsense and create
+        * one directly for this specific device/IOMMU combination...
+        */
+       domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+
+       if (!domain)
+               goto out_free_dma_domain;
+       domain->ops = ops;

drivers/iommu/dma-iommu.c new file +55 -0

+               goto out_free_iommu_domain;
+       }
+       /* ...then finally give it a kicking to make sure it fits */
+       dg->aperture_start = max(base, dg->aperture_start);
+       dg->aperture_end = min(base + size - 1, dg->aperture_end);
+       /*
+        * Note that this almost certainly breaks the case where multiple
+        * devices with different DMA capabilities need to share a domain,
+        * but we don't have the necessary information to handle that here
+        * anyway - "proper" group and domain allocation needs to involve
+        * the IOMMU driver and a complete view of the bus.
+        */
+
+       iovad = kzalloc(sizeof(*iovad), GFP_KERNEL);
+       if (!iovad)
+               goto out_free_iommu_domain;
+
+       /* Use the smallest supported page size for IOVA granularity */
+       order = __ffs(ops->pgsize_bitmap);
+       base_pfn = max(dg->aperture_start >> order, (dma_addr_t)1);
+       end_pfn = dg->aperture_end >> order;
+       init_iova_domain(iovad, 1UL << order, base_pfn, end_pfn);
+
+       dom->domain = domain;
+       dom->iovad = iovad;
+       kref_init(&dom->kref);
+       pr_debug("domain %p created\n", dom);
+       return dom;
+
+out_free_iommu_domain:
+       kfree(domain);
+out_free_dma_domain:
+       kfree(dom);
+       return NULL;
+}
+
+static void iommu_dma_free_domain(struct kref *kref)
+{
+       struct iommu_dma_domain *dom;
+
+       dom = container_of(kref, struct iommu_dma_domain, kref);
+       put_iova_domain(dom->iovad);
+       iommu_domain_free(dom->domain);
+       kfree(dom);
+       pr_debug("domain %p freed\n", dom);
+}
+
+void iommu_dma_release_domain(struct iommu_dma_domain *dom)
+{
+       kref_put(&dom->kref, iommu_dma_free_domain);
+}
+
+struct iommu_domain *iommu_dma_raw_domain(struct iommu_dma_domain *dom)
+{
+       return dom ? dom->domain : NULL;

drivers/iommu/dma-iommu.c new file +7 -0

+       else
+               set_dma_domain(dev, dom);
+       pr_debug("%s%s attached to domain %p\n", dev_name(dev),
+                       ret?" *not*":"", dom);
+       return ret;
+}
+

Hi Robin,

Quoted 26 lines · Robin Murphy

Taking inspiration from the existing arch/arm code, break out some generic functions to interface the DMA-API to the IOMMU-API. This will do the bulk of the heavy lifting for IOMMU-backed dma-mapping.

Whilst this RFC series is aimed at enabling arm64, once any remaining obvious issues in the common code are addressed we can complete the refactoring by porting arch/arm over for a merge-worthy series.

Signed-off-by Robin Murphy <[email protected]>

---
  drivers/iommu/Kconfig     |   7 +
  drivers/iommu/Makefile    |   1 +
  drivers/iommu/dma-iommu.c | 552 ++++++++++++++++++++++++++++++++++++++++++++++
  include/linux/dma-iommu.h |  94 ++++++++
  4 files changed, 654 insertions(+)

create mode 100644 drivers/iommu/dma-iommu.c
create mode 100644 include/linux/dma-iommu.h

drivers/iommu/Kconfig +0 -0

index a839ca9..19027bb 100644
@@ -20,6 +20,13 @@ config OF_IOMMU
         def_bool y
         depends on OF && IOMMU_API
 

drivers/iommu/Kconfig config OF_IOMMU · line 25

Quoted 3 lines

drivers/iommu/Kconfig +3 -0

+# IOMMU-agnostic DMA-mapping layer
+config IOMMU_DMA
+       def_bool n

This can just be `bool' (n is the default).

Quoted 60 lines

drivers/iommu/Kconfig +4 -0

+       depends on NEED_SG_DMA_LENGTH
+       select IOMMU_API
+       select IOMMU_IOVA
+
  config FSL_PAMU
         bool "Freescale IOMMU support"
         depends on PPC_E500MC

drivers/iommu/Makefile +1 -0

index 0b1b94e..37bfc4e 100644
@@ -1,6 +1,7 @@
  obj-$(CONFIG_IOMMU_API) += iommu.o
  obj-$(CONFIG_IOMMU_API) += iommu-traces.o
  obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
+obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
  obj-$(CONFIG_IOMMU_IOVA) += iova.o
  obj-$(CONFIG_OF_IOMMU) += of_iommu.o
  obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o msm_iommu_dev.o

drivers/iommu/dma-iommu.c new file +35 -0

new file mode 100644
index 0000000..b97cc0b9
@@ -0,0 +1,552 @@
+/*
+ * A fairly generic DMA-API to IOMMU-API glue layer.
+ *
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * based in part on arch/arm/mm/dma-mapping.c:
+ * Copyright (C) 2000-2004 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define pr_fmt(fmt)    "%s: " fmt, __func__
+
+#include <linux/dma-contiguous.h>
+#include <linux/dma-iommu.h>
+#include <linux/iova.h>
+
+int iommu_dma_init(void)
+{
+       return iommu_iova_cache_init();
+}
+
+struct iommu_dma_domain {
+       struct iommu_domain *domain;
+       struct iova_domain *iovad;

drivers/iommu/dma-iommu.c line 41

Quoted 6 lines

drivers/iommu/dma-iommu.c new file +6 -0

+       struct kref kref;
+};
+
+static inline dma_addr_t dev_dma_addr(struct device *dev, dma_addr_t addr)
+{
+       BUG_ON(addr < dev->dma_pfn_offset);

Shouldn't we convert the pfn_offset to an address before this check?

Quoted 13 lines

drivers/iommu/dma-iommu.c new file +13 -0

+       return addr - ((dma_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
+}
+
+static int __dma_direction_to_prot(enum dma_data_direction dir, bool coherent)
+{
+       int prot = coherent ? IOMMU_CACHE : 0;
+
+       switch (dir) {
+       case DMA_BIDIRECTIONAL:
+               return prot | IOMMU_READ | IOMMU_WRITE;
+       case DMA_TO_DEVICE:
+               return prot | IOMMU_READ;
+       case DMA_FROM_DEVICE:

drivers/iommu/dma-iommu.c line 59

Quoted 5 lines

drivers/iommu/dma-iommu.c new file +5 -0

+               return prot | IOMMU_WRITE;
+       default:
+               return 0;
+       }
+}

We could actually stick this into a header file as a generic helper. arch/arm/ already uses its own flavour, for example.

drivers/iommu/dma-iommu.c line 68

Quoted 8 lines

drivers/iommu/dma-iommu.c new file +8 -0

+static struct iova *__alloc_iova(struct device *dev, size_t size, bool coherent)
+{
+       struct iommu_dma_domain *dom = get_dma_domain(dev);
+       struct iova_domain *iovad = dom->iovad;
+       unsigned long shift = iova_shift(iovad);
+       unsigned long length = iova_align(iovad, size) >> shift;
+       unsigned long limit_pfn = iovad->dma_32bit_pfn;
+       u64 dma_limit = coherent ? dev->coherent_dma_mask : *dev->dma_mask;

Should we use dma_get_mask in the non-coherent case in case the mask pointer is NULL?

drivers/iommu/dma-iommu.c line 70

Quoted 1 line

drivers/iommu/dma-iommu.c new file +1 -0

+       limit_pfn = min(limit_pfn, (unsigned long)(dma_limit >> shift));

min_t avoids the explicit cast.

Quoted 6 lines

drivers/iommu/dma-iommu.c new file +5 -0

+       /* Alignment should probably come from a domain/device attribute... */
+       return alloc_iova(iovad, length, limit_pfn, false);
+}
+
+/*

drivers/iommu/dma-iommu.c line 85

Quoted 10 lines

drivers/iommu/dma-iommu.c new file +10 -0

+ * Create a mapping in device IO address space for specified pages
+ */
+dma_addr_t iommu_dma_create_iova_mapping(struct device *dev,
+               struct page **pages, size_t size, bool coherent)
+{
+       struct iommu_dma_domain *dom = get_dma_domain(dev);
+       struct iova_domain *iovad = dom->iovad;
+       struct iommu_domain *domain = dom->domain;
+       struct iova *iova;
+       unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

Why not just make the size parameter npages instead?

Quoted 18 lines

drivers/iommu/dma-iommu.c new file +18 -0

+       dma_addr_t addr_lo, addr_hi;
+       int i, prot = __dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent);
+
+       iova = __alloc_iova(dev, size, coherent);
+       if (!iova)
+               return DMA_ERROR_CODE;
+
+       addr_hi = addr_lo = iova_dma_addr(iovad, iova);
+       for (i = 0; i < count; ) {
+               unsigned int next_pfn = page_to_pfn(pages[i]) + 1;
+               phys_addr_t phys = page_to_phys(pages[i]);
+               unsigned int len, j;
+
+               for (j = i+1; j < count; j++, next_pfn++)
+                       if (page_to_pfn(pages[j]) != next_pfn)
+                               break;
+
+               len = (j - i) << PAGE_SHIFT;

drivers/iommu/dma-iommu.c line 108

Quoted 5 lines

drivers/iommu/dma-iommu.c new file +5 -0

+               if (iommu_map(domain, addr_hi, phys, len, prot))
+                       goto fail;
+               addr_hi += len;
+               i = j;
+       }

This loop is pretty miserable to read. Could we pass this off to ->map_sg and avoid the need to check that the pfns are contiguous?

Quoted 44 lines

drivers/iommu/dma-iommu.c new file +43 -0

+       return dev_dma_addr(dev, addr_lo);
+fail:
+       iommu_unmap(domain, addr_lo, addr_hi - addr_lo);
+       __free_iova(iovad, iova);
+       return DMA_ERROR_CODE;
+}
+
+int iommu_dma_release_iova_mapping(struct device *dev, dma_addr_t iova,
+               size_t size)
+{
+       struct iommu_dma_domain *dom = get_dma_domain(dev);
+       struct iova_domain *iovad = dom->iovad;
+       size_t offset = iova_offset(iovad, iova);
+       size_t len = iova_align(iovad, size + offset);
+
+       iommu_unmap(dom->domain, iova - offset, len);
+       free_iova(iovad, iova_pfn(iovad, iova));
+       return 0;
+}
+
+struct page **iommu_dma_alloc_buffer(struct device *dev, size_t size,
+               gfp_t gfp, struct dma_attrs *attrs,
+               void (clear_buffer)(struct page *page, size_t size))
+{
+       struct page **pages;
+       int count = size >> PAGE_SHIFT;
+       int array_size = count * sizeof(struct page *);
+       int i = 0;
+
+       if (array_size <= PAGE_SIZE)
+               pages = kzalloc(array_size, GFP_KERNEL);
+       else
+               pages = vzalloc(array_size);
+       if (!pages)
+               return NULL;
+
+       if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs)) {
+               unsigned long order = get_order(size);
+               struct page *page;
+
+               page = dma_alloc_from_contiguous(dev, count, order);
+               if (!page)
+                       goto error;

drivers/iommu/dma-iommu.c line 154

Quoted 3 lines

drivers/iommu/dma-iommu.c new file +3 -0

+
+               if (clear_buffer)
+                       clear_buffer(page, size);

For cache-coherent systems, this is just a memset so perhaps we could default to that if no function pointer is passed? It would also be cool to do the highmem vs lowmem stuff in core code, but that's more fiddly than it looks and probably not worth the hassle.

drivers/iommu/dma-iommu.c line 428

Quoted 10 lines

drivers/iommu/dma-iommu.c new file +10 -0

+struct iommu_dma_domain *iommu_dma_create_domain(const struct iommu_ops *ops,
+               dma_addr_t base, size_t size)
+{
+       struct iommu_dma_domain *dom;
+       struct iommu_domain *domain;
+       struct iova_domain *iovad;
+       struct iommu_domain_geometry *dg;
+       unsigned long order, base_pfn, end_pfn;
+
+       pr_debug("base=%pad\tsize=0x%zx\n", &base, size);

We can lose the debug prints for upstream.

Quoted 18 lines

drivers/iommu/dma-iommu.c new file +18 -0

+       dom = kzalloc(sizeof(*dom), GFP_KERNEL);
+       if (!dom)
+               return NULL;
+
+       /*
+        * HACK: We'd like to ask the relevant IOMMU in ops for a suitable
+        * domain, but until that happens, bypass the bus nonsense and create
+        * one directly for this specific device/IOMMU combination...
+        */
+       domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+
+       if (!domain)
+               goto out_free_dma_domain;
+       domain->ops = ops;
+
+       if (ops->domain_init(domain))
+               goto out_free_iommu_domain;
+       /*

drivers/iommu/dma-iommu.c line 452

Quoted 6 lines

drivers/iommu/dma-iommu.c new file +6 -0

+        * ...and do the bare minimum to sanity-check that the domain allows
+        * at least some access to the device...
+        */
+       dg = &domain->geometry;
+       if (!(base <= dg->aperture_end && base + size > dg->aperture_start)) {
+               pr_warn("DMA range outside IOMMU capability; is DT correct?\n");

We probably shouldn't print things about DT in core (non-OF) code.

Quoted 59 lines

drivers/iommu/dma-iommu.c new file +59 -0

+               goto out_free_iommu_domain;
+       }
+       /* ...then finally give it a kicking to make sure it fits */
+       dg->aperture_start = max(base, dg->aperture_start);
+       dg->aperture_end = min(base + size - 1, dg->aperture_end);
+       /*
+        * Note that this almost certainly breaks the case where multiple
+        * devices with different DMA capabilities need to share a domain,
+        * but we don't have the necessary information to handle that here
+        * anyway - "proper" group and domain allocation needs to involve
+        * the IOMMU driver and a complete view of the bus.
+        */
+
+       iovad = kzalloc(sizeof(*iovad), GFP_KERNEL);
+       if (!iovad)
+               goto out_free_iommu_domain;
+
+       /* Use the smallest supported page size for IOVA granularity */
+       order = __ffs(ops->pgsize_bitmap);
+       base_pfn = max(dg->aperture_start >> order, (dma_addr_t)1);
+       end_pfn = dg->aperture_end >> order;
+       init_iova_domain(iovad, 1UL << order, base_pfn, end_pfn);
+
+       dom->domain = domain;
+       dom->iovad = iovad;
+       kref_init(&dom->kref);
+       pr_debug("domain %p created\n", dom);
+       return dom;
+
+out_free_iommu_domain:
+       kfree(domain);
+out_free_dma_domain:
+       kfree(dom);
+       return NULL;
+}
+
+static void iommu_dma_free_domain(struct kref *kref)
+{
+       struct iommu_dma_domain *dom;
+
+       dom = container_of(kref, struct iommu_dma_domain, kref);
+       put_iova_domain(dom->iovad);
+       iommu_domain_free(dom->domain);
+       kfree(dom);
+       pr_debug("domain %p freed\n", dom);
+}
+
+void iommu_dma_release_domain(struct iommu_dma_domain *dom)
+{
+       kref_put(&dom->kref, iommu_dma_free_domain);
+}
+
+struct iommu_domain *iommu_dma_raw_domain(struct iommu_dma_domain *dom)
+{
+       return dom ? dom->domain : NULL;
+}
+
+int iommu_dma_attach_device(struct device *dev, struct iommu_dma_domain *dom)
+{

drivers/iommu/dma-iommu.c line 517

Quoted 6 lines

drivers/iommu/dma-iommu.c new file +6 -0

+       int ret;
+
+       kref_get(&dom->kref);
+       ret = iommu_attach_device(dom->domain, dev);
+       if (ret)
+               iommu_dma_release_domain(dom);

Shouldn't this be the responsibility of the caller?

Quoted 12 lines

drivers/iommu/dma-iommu.c new file +12 -0

+       else
+               set_dma_domain(dev, dom);
+       pr_debug("%s%s attached to domain %p\n", dev_name(dev),
+                       ret?" *not*":"", dom);
+       return ret;
+}
+
+void iommu_dma_detach_device(struct device *dev)
+{
+       struct iommu_dma_domain *dom = get_dma_domain(dev);
+
+       if (!dom) {

drivers/iommu/dma-iommu.c line 534

Quoted 5 lines

drivers/iommu/dma-iommu.c new file +5 -0

+               dev_warn(dev, "Not attached\n");
+               return;
+       }
+       set_dma_domain(dev, NULL);
+       iommu_detach_device(dom->domain, dev);

I think this means that we should be checking for NULL DMA domains in all of the IOVA calls, or can we assume our callers behave themselves?

drivers/iommu/dma-iommu.c line 546

Quoted 13 lines

drivers/iommu/dma-iommu.c new file +12 -0

+       iommu_dma_release_domain(dom);
+       pr_debug("%s detached from domain %p\n", dev_name(dev), dom);
+}
+
+int iommu_dma_supported(struct device *dev, u64 mask)
+{
+       /*
+        * This looks awful, but really it's reasonable to assume that if an
+        * IOMMU can't address everything that the CPU can, it probably isn't
+        * generic enough to be using this implementation in the first place.
+        */
+       return 1;

Hmm, perhaps, but I don't think it's *completely* unrealistic to have an IOMMU with more limited physical addressing caps than the CPU. Maybe we could have an IOMMU callback for querying the addressing capabilities?

It shouldn't block this series, I'm just interested in your thoughts on solving this in the future.

Taking inspiration from the existing arch/arm code, break out some generic functions to interface the DMA-API to the IOMMU-API. This will do the bulk of the heavy lifting for IOMMU-backed dma-mapping.

Whilst this RFC series is aimed at enabling arm64, once any remaining obvious issues in the common code are addressed we can complete the refactoring by porting arch/arm over for a merge-worthy series.

Signed-off-by Robin Murphy <[email protected]>

---
  drivers/iommu/Kconfig     |   7 +
  drivers/iommu/Makefile    |   1 +
  drivers/iommu/dma-iommu.c | 552 ++++++++++++++++++++++++++++++++++++++++++++++
  include/linux/dma-iommu.h |  94 ++++++++
  4 files changed, 654 insertions(+)

create mode 100644 drivers/iommu/dma-iommu.c
create mode 100644 include/linux/dma-iommu.h

drivers/iommu/Kconfig +7 -0

index a839ca9..19027bb 100644
@@ -20,6 +20,13 @@ config OF_IOMMU
         def_bool y
         depends on OF && IOMMU_API
 
+# IOMMU-agnostic DMA-mapping layer
+config IOMMU_DMA
+	def_bool n
+	depends on NEED_SG_DMA_LENGTH
+	select IOMMU_API
+	select IOMMU_IOVA
+
  config FSL_PAMU
  	bool "Freescale IOMMU support"
  	depends on PPC_E500MC

drivers/iommu/Makefile +1 -0

index 0b1b94e..37bfc4e 100644
@@ -1,6 +1,7 @@
  obj-$(CONFIG_IOMMU_API) += iommu.o
  obj-$(CONFIG_IOMMU_API) += iommu-traces.o
  obj-$(CONFIG_IOMMU_API) += iommu-sysfs.o
+obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o
  obj-$(CONFIG_IOMMU_IOVA) += iova.o
  obj-$(CONFIG_OF_IOMMU)	+= of_iommu.o
  obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o msm_iommu_dev.o

drivers/iommu/dma-iommu.c new file +62 -0

new file mode 100644
index 0000000..b97cc0b9
@@ -0,0 +1,552 @@
+/*
+ * A fairly generic DMA-API to IOMMU-API glue layer.
+ *
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * based in part on arch/arm/mm/dma-mapping.c:
+ * Copyright (C) 2000-2004 Russell King
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define pr_fmt(fmt)	"%s: " fmt, __func__
+
+#include <linux/dma-contiguous.h>
+#include <linux/dma-iommu.h>
+#include <linux/iova.h>
+
+int iommu_dma_init(void)
+{
+	return iommu_iova_cache_init();
+}
+
+struct iommu_dma_domain {
+	struct iommu_domain *domain;
+	struct iova_domain *iovad;
+	struct kref kref;
+};
+
+static inline dma_addr_t dev_dma_addr(struct device *dev, dma_addr_t addr)
+{
+	BUG_ON(addr < dev->dma_pfn_offset);
+	return addr - ((dma_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
+}
+
+static int __dma_direction_to_prot(enum dma_data_direction dir, bool coherent)
+{
+	int prot = coherent ? IOMMU_CACHE : 0;
+
+	switch (dir) {
+	case DMA_BIDIRECTIONAL:
+		return prot | IOMMU_READ | IOMMU_WRITE;
+	case DMA_TO_DEVICE:
+		return prot | IOMMU_READ;
+	case DMA_FROM_DEVICE:
+		return prot | IOMMU_WRITE;
+	default:
+		return 0;
+	}
+}
+
+static struct iova *__alloc_iova(struct device *dev, size_t size, bool coherent)
+{

drivers/iommu/dma-iommu.c new file +480 -0

+}
+
+/*
+ * Create a mapping in device IO address space for specified pages
+ */
+dma_addr_t iommu_dma_create_iova_mapping(struct device *dev,
+		struct page **pages, size_t size, bool coherent)
+{
+	struct iommu_dma_domain *dom = get_dma_domain(dev);
+	struct iova_domain *iovad = dom->iovad;
+	struct iommu_domain *domain = dom->domain;
+	struct iova *iova;
+	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+	dma_addr_t addr_lo, addr_hi;
+	int i, prot = __dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent);
+
+	iova = __alloc_iova(dev, size, coherent);
+	if (!iova)
+		return DMA_ERROR_CODE;
+
+	addr_hi = addr_lo = iova_dma_addr(iovad, iova);
+	for (i = 0; i < count; ) {
+		unsigned int next_pfn = page_to_pfn(pages[i]) + 1;
+		phys_addr_t phys = page_to_phys(pages[i]);
+		unsigned int len, j;
+
+		for (j = i+1; j < count; j++, next_pfn++)
+			if (page_to_pfn(pages[j]) != next_pfn)
+				break;
+
+		len = (j - i) << PAGE_SHIFT;
+		if (iommu_map(domain, addr_hi, phys, len, prot))
+			goto fail;
+		addr_hi += len;
+		i = j;
+	}
+	return dev_dma_addr(dev, addr_lo);
+fail:
+	iommu_unmap(domain, addr_lo, addr_hi - addr_lo);
+	__free_iova(iovad, iova);
+	return DMA_ERROR_CODE;
+}
+
+int iommu_dma_release_iova_mapping(struct device *dev, dma_addr_t iova,
+		size_t size)
+{
+	struct iommu_dma_domain *dom = get_dma_domain(dev);
+	struct iova_domain *iovad = dom->iovad;
+	size_t offset = iova_offset(iovad, iova);
+	size_t len = iova_align(iovad, size + offset);
+
+	iommu_unmap(dom->domain, iova - offset, len);
+	free_iova(iovad, iova_pfn(iovad, iova));
+	return 0;
+}
+
+struct page **iommu_dma_alloc_buffer(struct device *dev, size_t size,
+		gfp_t gfp, struct dma_attrs *attrs,
+		void (clear_buffer)(struct page *page, size_t size))
+{
+	struct page **pages;
+	int count = size >> PAGE_SHIFT;
+	int array_size = count * sizeof(struct page *);
+	int i = 0;
+
+	if (array_size <= PAGE_SIZE)
+		pages = kzalloc(array_size, GFP_KERNEL);
+	else
+		pages = vzalloc(array_size);
+	if (!pages)
+		return NULL;
+
+	if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs)) {
+		unsigned long order = get_order(size);
+		struct page *page;
+
+		page = dma_alloc_from_contiguous(dev, count, order);
+		if (!page)
+			goto error;
+
+		if (clear_buffer)
+			clear_buffer(page, size);
+
+		for (i = 0; i < count; i++)
+			pages[i] = page + i;
+
+		return pages;
+	}
+
+	/*
+	 * IOMMU can map any pages, so himem can also be used here
+	 */
+	gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
+
+	while (count) {
+		int j, order = __fls(count);
+
+		pages[i] = alloc_pages(gfp, order);
+		while (!pages[i] && order)
+			pages[i] = alloc_pages(gfp, --order);
+		if (!pages[i])
+			goto error;
+
+		if (order) {
+			split_page(pages[i], order);
+			j = 1 << order;
+			while (--j)
+				pages[i + j] = pages[i] + j;
+		}
+
+		if (clear_buffer)
+			clear_buffer(pages[i], PAGE_SIZE << order);
+		i += 1 << order;
+		count -= 1 << order;
+	}
+
+	return pages;
+error:
+	while (i--)
+		if (pages[i])
+			__free_pages(pages[i], 0);
+	if (array_size <= PAGE_SIZE)
+		kfree(pages);
+	else
+		vfree(pages);
+	return NULL;
+}
+
+int iommu_dma_free_buffer(struct device *dev, struct page **pages, size_t size,
+		struct dma_attrs *attrs)
+{
+	int count = size >> PAGE_SHIFT;
+	int array_size = count * sizeof(struct page *);
+	int i;
+
+	if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs)) {
+		dma_release_from_contiguous(dev, pages[0], count);
+	} else {
+		for (i = 0; i < count; i++)
+			if (pages[i])
+				__free_pages(pages[i], 0);
+	}
+
+	if (array_size <= PAGE_SIZE)
+		kfree(pages);
+	else
+		vfree(pages);
+	return 0;
+}
+
+static dma_addr_t __iommu_dma_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		bool coherent)
+{
+	dma_addr_t dma_addr;
+	struct iommu_dma_domain *dom = get_dma_domain(dev);
+	struct iova_domain *iovad = dom->iovad;
+	phys_addr_t phys = page_to_phys(page) + offset;
+	size_t iova_off = iova_offset(iovad, phys);
+	size_t len = iova_align(iovad, size + iova_off);
+	int prot = __dma_direction_to_prot(dir, coherent);
+	struct iova *iova = __alloc_iova(dev, len, coherent);
+
+	if (!iova)
+		return DMA_ERROR_CODE;
+
+	dma_addr = iova_dma_addr(iovad, iova);
+	if (iommu_map(dom->domain, dma_addr, phys - iova_off, len, prot)) {
+		__free_iova(iovad, iova);
+		return DMA_ERROR_CODE;
+	}
+
+	return dev_dma_addr(dev, dma_addr + iova_off);
+}
+
+dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		struct dma_attrs *attrs)
+{
+	return __iommu_dma_map_page(dev, page, offset, size, dir, false);
+}
+
+dma_addr_t iommu_dma_coherent_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		struct dma_attrs *attrs)
+{
+	return __iommu_dma_map_page(dev, page, offset, size, dir, true);
+}
+
+void iommu_dma_unmap_page(struct device *dev, dma_addr_t handle, size_t size,
+		enum dma_data_direction dir, struct dma_attrs *attrs)
+{
+	struct iommu_dma_domain *dom = get_dma_domain(dev);
+	struct iova_domain *iovad = dom->iovad;
+	size_t offset = iova_offset(iovad, handle);
+	size_t len = iova_align(iovad, size + offset);
+	dma_addr_t iova = handle - offset;
+
+	if (!iova)
+		return;
+
+	iommu_unmap(dom->domain, iova, len);
+	free_iova(iovad, iova_pfn(iovad, iova));
+}
+
+static int finalise_sg(struct device *dev, struct scatterlist *sg, int nents,
+		dma_addr_t dma_addr)
+{
+	struct scatterlist *s, *seg = sg;
+	unsigned long seg_mask = dma_get_seg_boundary(dev);
+	unsigned int max_len = dma_get_max_seg_size(dev);
+	unsigned int seg_len = 0, seg_dma = 0;
+	int i, count = 1;
+
+	for_each_sg(sg, s, nents, i) {
+		/* Un-swizzling the fields here, hence the naming mismatch */
+		unsigned int s_offset = sg_dma_address(s);
+		unsigned int s_length = sg_dma_len(s);
+		unsigned int s_dma_len = s->length;
+
+		s->offset = s_offset;
+		s->length = s_length;
+		sg_dma_address(s) = DMA_ERROR_CODE;
+		sg_dma_len(s) = 0;
+
+		if (seg_len && (seg_dma + seg_len == dma_addr + s_offset) &&
+		    (seg_len + s_dma_len <= max_len) &&
+		    ((seg_dma & seg_mask) <= seg_mask - (seg_len + s_length))
+		   ) {
+			sg_dma_len(seg) += s_dma_len;
+		} else {
+			if (seg_len) {
+				seg = sg_next(seg);
+				count++;
+			}
+			sg_dma_len(seg) = s_dma_len;
+			sg_dma_address(seg) = dma_addr + s_offset;
+
+			seg_len = s_offset;
+			seg_dma = dma_addr + s_offset;
+		}
+		seg_len += s_length;
+		dma_addr += s_dma_len;
+	}
+	return count;
+}
+
+static void invalidate_sg(struct scatterlist *sg, int nents)
+{
+	struct scatterlist *s;
+	int i;
+
+	for_each_sg(sg, s, nents, i) {
+		if (sg_dma_address(s) != DMA_ERROR_CODE)
+			s->offset = sg_dma_address(s);
+		if (sg_dma_len(s))
+			s->length = sg_dma_len(s);
+		sg_dma_address(s) = DMA_ERROR_CODE;
+		sg_dma_len(s) = 0;
+	}
+}
+
+static int __iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
+		int nents, enum dma_data_direction dir, struct dma_attrs *attrs,
+		bool coherent)
+{
+	struct iommu_dma_domain *dom = get_dma_domain(dev);
+	struct iova_domain *iovad = dom->iovad;
+	struct iova *iova;
+	struct scatterlist *s;
+	dma_addr_t dma_addr;
+	size_t iova_len = 0;
+	int i, prot = __dma_direction_to_prot(dir, coherent);
+
+	/*
+	 * Work out how much IOVA space we need, and align the segments to
+	 * IOVA granules for the IOMMU driver to handle. With some clever
+	 * trickery we can modify the list in a reversible manner.
+	 */
+	for_each_sg(sg, s, nents, i) {
+		size_t s_offset = iova_offset(iovad, s->offset);
+		size_t s_length = s->length;
+
+		sg_dma_address(s) = s->offset;
+		sg_dma_len(s) = s_length;
+		s->offset -= s_offset;
+		s_length = iova_align(iovad, s_length + s_offset);
+		s->length = s_length;
+
+		iova_len += s_length;
+	}
+
+	iova = __alloc_iova(dev, iova_len, coherent);
+	if (!iova)
+		goto out_restore_sg;
+
+	/*
+	 * We'll leave any physical concatenation to the IOMMU driver's
+	 * implementation - it knows better than we do.
+	 */
+	dma_addr = iova_dma_addr(iovad, iova);
+	if (iommu_map_sg(dom->domain, dma_addr, sg, nents, prot) < iova_len)
+		goto out_free_iova;
+
+	return finalise_sg(dev, sg, nents, dev_dma_addr(dev, dma_addr));
+
+out_free_iova:
+	__free_iova(iovad, iova);
+out_restore_sg:
+	invalidate_sg(sg, nents);
+	return 0;
+}
+
+int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
+		enum dma_data_direction dir, struct dma_attrs *attrs)
+{
+	return __iommu_dma_map_sg(dev, sg, nents, dir, attrs, false);
+}
+
+int iommu_dma_coherent_map_sg(struct device *dev, struct scatterlist *sg,
+		int nents, enum dma_data_direction dir, struct dma_attrs *attrs)
+{
+	return __iommu_dma_map_sg(dev, sg, nents, dir, attrs, true);
+}
+
+void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
+		enum dma_data_direction dir, struct dma_attrs *attrs)
+{
+	struct iommu_dma_domain *dom = get_dma_domain(dev);
+	struct iova_domain *iovad = dom->iovad;
+	struct scatterlist *s;
+	int i;
+	dma_addr_t iova = sg_dma_address(sg) & ~iova_mask(iovad);
+	size_t len = 0;
+
+	/*
+	 * The scatterlist segments are mapped into contiguous IOVA space,
+	 * so just add up the total length and unmap it in one go.
+	 */
+	for_each_sg(sg, s, nents, i)
+		len += sg_dma_len(s);
+
+	iommu_unmap(dom->domain, iova, len);
+	free_iova(iovad, iova_pfn(iovad, iova));
+}
+
+struct iommu_dma_domain *iommu_dma_create_domain(const struct iommu_ops *ops,
+		dma_addr_t base, size_t size)
+{
+	struct iommu_dma_domain *dom;
+	struct iommu_domain *domain;
+	struct iova_domain *iovad;
+	struct iommu_domain_geometry *dg;
+	unsigned long order, base_pfn, end_pfn;
+
+	pr_debug("base=%pad\tsize=0x%zx\n", &base, size);
+	dom = kzalloc(sizeof(*dom), GFP_KERNEL);
+	if (!dom)
+		return NULL;
+
+	/*
+	 * HACK: We'd like to ask the relevant IOMMU in ops for a suitable
+	 * domain, but until that happens, bypass the bus nonsense and create
+	 * one directly for this specific device/IOMMU combination...
+	 */
+	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+
+	if (!domain)
+		goto out_free_dma_domain;
+	domain->ops = ops;
+
+	if (ops->domain_init(domain))
+		goto out_free_iommu_domain;
+	/*
+	 * ...and do the bare minimum to sanity-check that the domain allows
+	 * at least some access to the device...
+	 */
+	dg = &domain->geometry;
+	if (!(base <= dg->aperture_end && base + size > dg->aperture_start)) {
+		pr_warn("DMA range outside IOMMU capability; is DT correct?\n");
+		goto out_free_iommu_domain;
+	}
+	/* ...then finally give it a kicking to make sure it fits */
+	dg->aperture_start = max(base, dg->aperture_start);
+	dg->aperture_end = min(base + size - 1, dg->aperture_end);
+	/*
+	 * Note that this almost certainly breaks the case where multiple
+	 * devices with different DMA capabilities need to share a domain,
+	 * but we don't have the necessary information to handle that here
+	 * anyway - "proper" group and domain allocation needs to involve
+	 * the IOMMU driver and a complete view of the bus.
+	 */
+
+	iovad = kzalloc(sizeof(*iovad), GFP_KERNEL);
+	if (!iovad)
+		goto out_free_iommu_domain;
+
+	/* Use the smallest supported page size for IOVA granularity */
+	order = __ffs(ops->pgsize_bitmap);
+	base_pfn = max(dg->aperture_start >> order, (dma_addr_t)1);
+	end_pfn = dg->aperture_end >> order;
+	init_iova_domain(iovad, 1UL << order, base_pfn, end_pfn);
+
+	dom->domain = domain;
+	dom->iovad = iovad;
+	kref_init(&dom->kref);
+	pr_debug("domain %p created\n", dom);
+	return dom;
+
+out_free_iommu_domain:
+	kfree(domain);
+out_free_dma_domain:
+	kfree(dom);
+	return NULL;
+}
+
+static void iommu_dma_free_domain(struct kref *kref)
+{
+	struct iommu_dma_domain *dom;
+
+	dom = container_of(kref, struct iommu_dma_domain, kref);
+	put_iova_domain(dom->iovad);
+	iommu_domain_free(dom->domain);
+	kfree(dom);
+	pr_debug("domain %p freed\n", dom);
+}
+
+void iommu_dma_release_domain(struct iommu_dma_domain *dom)
+{
+	kref_put(&dom->kref, iommu_dma_free_domain);
+}
+
+struct iommu_domain *iommu_dma_raw_domain(struct iommu_dma_domain *dom)
+{
+	return dom ? dom->domain : NULL;
+}
+
+int iommu_dma_attach_device(struct device *dev, struct iommu_dma_domain *dom)
+{
+	int ret;
+
+	kref_get(&dom->kref);
+	ret = iommu_attach_device(dom->domain, dev);
+	if (ret)
+		iommu_dma_release_domain(dom);
+	else
+		set_dma_domain(dev, dom);
+	pr_debug("%s%s attached to domain %p\n", dev_name(dev),
+			ret?" *not*":"", dom);
+	return ret;
+}
+
+void iommu_dma_detach_device(struct device *dev)
+{
+	struct iommu_dma_domain *dom = get_dma_domain(dev);
+
+	if (!dom) {
+		dev_warn(dev, "Not attached\n");
+		return;
+	}
+	set_dma_domain(dev, NULL);
+	iommu_detach_device(dom->domain, dev);
+	iommu_dma_release_domain(dom);
+	pr_debug("%s detached from domain %p\n", dev_name(dev), dom);
+}
+
+int iommu_dma_supported(struct device *dev, u64 mask)
+{
+	/*
+	 * This looks awful, but really it's reasonable to assume that if an
+	 * IOMMU can't address everything that the CPU can, it probably isn't
+	 * generic enough to be using this implementation in the first place.
+	 */
+	return 1;
+}
+
+int iommu_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
+{
+	return dma_addr == DMA_ERROR_CODE;
+}

include/linux/dma-iommu.h new file +84 -0

new file mode 100644
index 0000000..4bba85a
@@ -0,0 +1,94 @@
+/*
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __DMA_IOMMU_H
+#define __DMA_IOMMU_H
+
+#ifdef __KERNEL__
+
+#include <linux/types.h>
+#include <linux/iommu.h>
+
+#ifdef CONFIG_IOMMU_DMA
+
+int iommu_dma_init(void);
+
+
+struct iommu_dma_domain *iommu_dma_create_domain(const struct iommu_ops *ops,
+		dma_addr_t base, size_t size);
+void iommu_dma_release_domain(struct iommu_dma_domain *dma_domain);
+
+struct iommu_domain *iommu_dma_raw_domain(struct iommu_dma_domain *dma_domain);
+
+int iommu_dma_attach_device(struct device *dev, struct iommu_dma_domain *domain);
+void iommu_dma_detach_device(struct device *dev);
+
+/*
+ * Implementation of these is left to arch code - it can associate domains
+ * with devices however it likes, provided the lookup is efficient.
+ */
+struct iommu_dma_domain *get_dma_domain(struct device *dev);
+void set_dma_domain(struct device *dev, struct iommu_dma_domain *dma_domain);
+
+
+dma_addr_t iommu_dma_create_iova_mapping(struct device *dev,
+		struct page **pages, size_t size, bool coherent);
+int iommu_dma_release_iova_mapping(struct device *dev, dma_addr_t iova,
+		size_t size);
+
+struct page **iommu_dma_alloc_buffer(struct device *dev, size_t size,
+		gfp_t gfp, struct dma_attrs *attrs,
+		void (clear_buffer)(struct page *page, size_t size));
+int iommu_dma_free_buffer(struct device *dev, struct page **pages, size_t size,
+		struct dma_attrs *attrs);
+
+dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		struct dma_attrs *attrs);
+dma_addr_t iommu_dma_coherent_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		struct dma_attrs *attrs);
+void iommu_dma_unmap_page(struct device *dev, dma_addr_t handle, size_t size,
+		enum dma_data_direction dir, struct dma_attrs *attrs);
+
+int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
+		enum dma_data_direction dir, struct dma_attrs *attrs);
+int iommu_dma_coherent_map_sg(struct device *dev, struct scatterlist *sg,
+		int nents, enum dma_data_direction dir,
+		struct dma_attrs *attrs);
+void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sgl, int nents,
+		enum dma_data_direction dir, struct dma_attrs *attrs);
+
+int iommu_dma_supported(struct device *dev, u64 mask);
+int iommu_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
+
+#else
+
+static inline int iommu_dma_init(void)
+{
+	return 0;
+}
+
+static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)

Taking some inspiration from the arch/arm code, implement the arch-specific side of the DMA mapping ops using the new IOMMU-DMA layer.

Signed-off-by Robin Murphy <[email protected]>

---
 arch/arm64/include/asm/device.h      |   3 +
 arch/arm64/include/asm/dma-mapping.h |  17 ++
 arch/arm64/mm/dma-mapping.c          | 320 +++++++++++++++++++++++++++++++++++
 3 files changed, 340 insertions(+)

arch/arm64/include/asm/device.h +3 -0

index 243ef25..510cee1 100644
@@ -20,6 +20,9 @@ struct dev_archdata {
 	struct dma_map_ops *dma_ops;
 #ifdef CONFIG_IOMMU_API
 	void *iommu;			/* private IOMMU data */
+#ifdef CONFIG_IOMMU_DMA
+	struct iommu_dma_domain *dma_domain;
+#endif
 #endif
 	bool dma_coherent;
 };

arch/arm64/include/asm/dma-mapping.h +0 -0

index 6932bb5..c1b271f 100644

arch/arm64/include/asm/dma-mapping.h +11 -0

+static inline void set_dma_domain(struct device *dev,
+				  struct iommu_dma_domain *dma_domain)
+{
+	dev->archdata.dma_domain = dma_domain;
+}
+#endif
+
 static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
 {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return DMA_ERROR_CODE;
 	return (dma_addr_t)paddr;
 }
 
 static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
 {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return 0;
 	return (phys_addr_t)dev_addr;
 }
 

arch/arm64/mm/dma-mapping.c +45 -0

index 0a24b9b..28e771c 100644
@@ -23,6 +23,7 @@
 #include <linux/genalloc.h>
 #include <linux/dma-mapping.h>
 #include <linux/dma-contiguous.h>
+#include <linux/dma-iommu.h>
 #include <linux/vmalloc.h>
 #include <linux/swiotlb.h>
 

@@ -426,6 +427,7 @@ static int __init arm64_dma_init(void)
 
 	ret |= swiotlb_late_init();
 	ret |= atomic_pool_init();
+	ret |= iommu_dma_init();
 
 	return ret;
 }

@@ -439,3 +441,321 @@ static int __init dma_debug_do_init(void)
 	return 0;
 }
 fs_initcall(dma_debug_do_init);
+
+
+#ifdef CONFIG_IOMMU_DMA
+
+static struct page **__atomic_get_pages(void *addr)
+{
+	struct page *page;
+	phys_addr_t phys;
+
+	phys = gen_pool_virt_to_phys(atomic_pool, (unsigned long)addr);
+	page = phys_to_page(phys);
+
+	return (struct page **)page;
+}
+
+static struct page **__iommu_get_pages(void *cpu_addr, struct dma_attrs *attrs)
+{
+	struct vm_struct *area;
+
+	if (__in_atomic_pool(cpu_addr, PAGE_SIZE))
+		return __atomic_get_pages(cpu_addr);
+
+	area = find_vm_area(cpu_addr);
+	if (!area)
+		return NULL;
+
+	return area->pages;
+}
+
+static void *__iommu_alloc_atomic(struct device *dev, size_t size,
+				  dma_addr_t *handle, bool coherent)
+{
+	struct page *page;
+	void *addr;
+
+	addr = __alloc_from_pool(size, &page);
+	if (!addr)
+		return NULL;
+
+	*handle = iommu_dma_create_iova_mapping(dev, &page, size, coherent);
+	if (*handle == DMA_ERROR_CODE) {
+		__free_from_pool(addr, size);
+		return NULL;

arch/arm64/mm/dma-mapping.c +23 -0

+static void __dma_clear_buffer(struct page *page, size_t size)
+{
+	void *ptr = page_address(page);
+
+	memset(ptr, 0, size);
+	__dma_flush_range(ptr, ptr + size);
+}
+
+static void *__iommu_alloc_attrs(struct device *dev, size_t size,
+				 dma_addr_t *handle, gfp_t gfp,
+				 struct dma_attrs *attrs)
+{
+	bool coherent = is_device_dma_coherent(dev);
+	pgprot_t prot = coherent ? __pgprot(PROT_NORMAL) :
+				   __pgprot(PROT_NORMAL_NC);
+	struct page **pages;
+	void *addr = NULL;
+
+	*handle = DMA_ERROR_CODE;
+	size = PAGE_ALIGN(size);
+
+	if (!(gfp & __GFP_WAIT))
+		return __iommu_alloc_atomic(dev, size, handle, coherent);

Quoted 2 lines · Robin Murphy

Taking some inspiration from the arch/arm code, implement the arch-specific side of the DMA mapping ops using the new IOMMU-DMA layer.

Is anybody looking at porting arch/arm/ over to this?

Quoted 30 lines

Signed-off-by Robin Murphy <[email protected]>

---
  arch/arm64/include/asm/device.h      |   3 +
  arch/arm64/include/asm/dma-mapping.h |  17 ++
  arch/arm64/mm/dma-mapping.c          | 320 +++++++++++++++++++++++++++++++++++
  3 files changed, 340 insertions(+)

arch/arm64/include/asm/device.h +3 -0

index 243ef25..510cee1 100644
@@ -20,6 +20,9 @@ struct dev_archdata {
  	struct dma_map_ops *dma_ops;
  #ifdef CONFIG_IOMMU_API
  	void *iommu;			/* private IOMMU data */
+#ifdef CONFIG_IOMMU_DMA
+	struct iommu_dma_domain *dma_domain;
+#endif
  #endif
  	bool dma_coherent;
  };

arch/arm64/include/asm/dma-mapping.h +0 -0

index 6932bb5..c1b271f 100644
@@ -62,13 +62,30 @@ static inline bool is_device_dma_coherent(struct device *dev)
 
  #include <asm-generic/dma-mapping-common.h>
 

arch/arm64/include/asm/dma-mapping.h static inline bool is_device_dma_coherent(struct device *dev) · line 69

Quoted 5 lines

arch/arm64/include/asm/dma-mapping.h +5 -0

+#ifdef CONFIG_IOMMU_DMA
+static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)
+{
+	return dev->archdata.dma_domain;
+}

You use this function in patch 1, so you probably need to reorder the series slightly.

Quoted 93 lines

arch/arm64/include/asm/dma-mapping.h +11 -0

+static inline void set_dma_domain(struct device *dev,
+				  struct iommu_dma_domain *dma_domain)
+{
+	dev->archdata.dma_domain = dma_domain;
+}
+#endif
+
  static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
  {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return DMA_ERROR_CODE;
  	return (dma_addr_t)paddr;
  }
 
  static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
  {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return 0;
  	return (phys_addr_t)dev_addr;
  }
 

arch/arm64/mm/dma-mapping.c +50 -0

index 0a24b9b..28e771c 100644
@@ -23,6 +23,7 @@
  #include <linux/genalloc.h>
  #include <linux/dma-mapping.h>
  #include <linux/dma-contiguous.h>
+#include <linux/dma-iommu.h>
  #include <linux/vmalloc.h>
  #include <linux/swiotlb.h>
 

@@ -426,6 +427,7 @@ static int __init arm64_dma_init(void)
 
  	ret |= swiotlb_late_init();
  	ret |= atomic_pool_init();
+	ret |= iommu_dma_init();
 
  	return ret;
  }

@@ -439,3 +441,321 @@ static int __init dma_debug_do_init(void)
  	return 0;
  }
  fs_initcall(dma_debug_do_init);
+
+
+#ifdef CONFIG_IOMMU_DMA
+
+static struct page **__atomic_get_pages(void *addr)
+{
+	struct page *page;
+	phys_addr_t phys;
+
+	phys = gen_pool_virt_to_phys(atomic_pool, (unsigned long)addr);
+	page = phys_to_page(phys);
+
+	return (struct page **)page;
+}
+
+static struct page **__iommu_get_pages(void *cpu_addr, struct dma_attrs *attrs)
+{
+	struct vm_struct *area;
+
+	if (__in_atomic_pool(cpu_addr, PAGE_SIZE))
+		return __atomic_get_pages(cpu_addr);
+
+	area = find_vm_area(cpu_addr);
+	if (!area)
+		return NULL;
+
+	return area->pages;
+}
+
+static void *__iommu_alloc_atomic(struct device *dev, size_t size,
+				  dma_addr_t *handle, bool coherent)
+{
+	struct page *page;
+	void *addr;
+
+	addr = __alloc_from_pool(size, &page);
+	if (!addr)
+		return NULL;
+
+	*handle = iommu_dma_create_iova_mapping(dev, &page, size, coherent);
+	if (*handle == DMA_ERROR_CODE) {
+		__free_from_pool(addr, size);
+		return NULL;
+	}
+	return addr;
+}
+
+static void __iommu_free_atomic(struct device *dev, void *cpu_addr,

arch/arm64/mm/dma-mapping.c static int __init dma_debug_do_init(void) · line 496

Quoted 5 lines

arch/arm64/mm/dma-mapping.c +5 -0

+				dma_addr_t handle, size_t size)
+{
+	iommu_dma_release_iova_mapping(dev, handle, size);
+	__free_from_pool(cpu_addr, size);
+}

Up until this point, I don't get why things need to be arch-specific. Surely we should only care about cache and MMU management in the arch code?

Quoted 28 lines

arch/arm64/mm/dma-mapping.c +28 -0

+static void __dma_clear_buffer(struct page *page, size_t size)
+{
+	void *ptr = page_address(page);
+
+	memset(ptr, 0, size);
+	__dma_flush_range(ptr, ptr + size);
+}
+
+static void *__iommu_alloc_attrs(struct device *dev, size_t size,
+				 dma_addr_t *handle, gfp_t gfp,
+				 struct dma_attrs *attrs)
+{
+	bool coherent = is_device_dma_coherent(dev);
+	pgprot_t prot = coherent ? __pgprot(PROT_NORMAL) :
+				   __pgprot(PROT_NORMAL_NC);
+	struct page **pages;
+	void *addr = NULL;
+
+	*handle = DMA_ERROR_CODE;
+	size = PAGE_ALIGN(size);
+
+	if (!(gfp & __GFP_WAIT))
+		return __iommu_alloc_atomic(dev, size, handle, coherent);
+	/*
+	 * FIXME: This isn't even true any more!
+	 *
+	 * Following is a work-around (a.k.a. hack) to prevent pages
+	 * with __GFP_COMP being passed to split_page() which cannot

arch/arm64/mm/dma-mapping.c static int __init dma_debug_do_init(void) · line 530

Quoted 5 lines

arch/arm64/mm/dma-mapping.c +5 -0

+	 * handle them.  The real problem is that this flag probably
+	 * should be 0 on ARM as it is not supported on this
+	 * platform; see CONFIG_HUGETLBFS.
+	 */
+	gfp &= ~(__GFP_COMP);

We should fix this... is it not just a case of calling split_huge_page for compond pages?

arch/arm64/include/asm/dma-mapping.h +9 -0

index 6932bb5..c1b271f 100644
@@ -62,13 +62,30 @@ static inline bool is_device_dma_coherent(struct device *dev)
 
 #include <asm-generic/dma-mapping-common.h>
 
+#ifdef CONFIG_IOMMU_DMA
+static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)
+{
+	return dev->archdata.dma_domain;
+}
+
+static inline void set_dma_domain(struct device *dev,
+				  struct iommu_dma_domain *dma_domain)
+{

On Fri, 2015-02-06 at 14:55 +0000, Robin Murphy wrote <...>

Quoted 17 lines

arch/arm64/include/asm/dma-mapping.h +9 -0

index 6932bb5..c1b271f 100644
@@ -62,13 +62,30 @@ static inline bool is_device_dma_coherent(struct device *dev)
 
  #include <asm-generic/dma-mapping-common.h>
 
+#ifdef CONFIG_IOMMU_DMA
+static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)
+{
+	return dev->archdata.dma_domain;
+}
+
+static inline void set_dma_domain(struct device *dev,
+				  struct iommu_dma_domain *dma_domain)
+{

arch/arm64/include/asm/dma-mapping.h static inline bool is_device_dma_coherent(struct device *dev) · line 83

Quoted 10 lines

arch/arm64/include/asm/dma-mapping.h +6 -0

+	dev->archdata.dma_domain = dma_domain;
+}
+#endif
+
  static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
  {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return DMA_ERROR_CODE;
  	return (dma_addr_t)paddr;
  }

Hi Robin,

Build fail if CONFIG_IOMMU_DMA is not enabled.

In file included from ../include/linux/dma-mapping.h:82:0,

                  from ../arch/arm64/kernel/asm-offsets.c:23:

../arch/arm64/include/asm/dma-mapping.h: In function 'phys_to_dma':
../arch/arm64/include/asm/dma-mapping.h:81:2: error: implicit declaration of function 'get_dma_domain' [-Werror=implicit-function-declaration]
if (WARN_ON(dev && get_dma_domain(dev)))
^

Joe.C

Quoted 42 lines · Yingjoe Chen

On Fri, 2015-02-06 at 14:55 +0000, Robin Murphy wrote <...>

Quoted 17 lines

arch/arm64/include/asm/dma-mapping.h +9 -0

index 6932bb5..c1b271f 100644
@@ -62,13 +62,30 @@ static inline bool is_device_dma_coherent(struct device *dev)
 
  #include <asm-generic/dma-mapping-common.h>
 
+#ifdef CONFIG_IOMMU_DMA
+static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)
+{
+	return dev->archdata.dma_domain;
+}
+
+static inline void set_dma_domain(struct device *dev,
+				  struct iommu_dma_domain *dma_domain)
+{

arch/arm64/include/asm/dma-mapping.h static inline bool is_device_dma_coherent(struct device *dev) · line 83

Quoted 10 lines

arch/arm64/include/asm/dma-mapping.h +6 -0

+	dev->archdata.dma_domain = dma_domain;
+}
+#endif
+
  static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
  {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return DMA_ERROR_CODE;
  	return (dma_addr_t)paddr;
  }

Hi Robin,

Build fail if CONFIG_IOMMU_DMA is not enabled.

In file included from ../include/linux/dma-mapping.h:82:0,

                  from ../arch/arm64/kernel/asm-offsets.c:23:

../arch/arm64/include/asm/dma-mapping.h: In function 'phys_to_dma':
../arch/arm64/include/asm/dma-mapping.h:81:2: error: implicit declaration of function 'get_dma_domain' [-Werror=implicit-function-declaration]
if (WARN_ON(dev && get_dma_domain(dev)))
^

Quoted 1 line

Joe.C

Bah, how did I manage to make such a half-finished mess of the includes? Current fixup diff below.

Thanks,
Robin.

Quoted 43 lines · Robin Murphy

Quoted 42 lines · Yingjoe Chen

On Fri, 2015-02-06 at 14:55 +0000, Robin Murphy wrote <...>

Quoted 17 lines

arch/arm64/include/asm/dma-mapping.h +9 -0

index 6932bb5..c1b271f 100644
@@ -62,13 +62,30 @@ static inline bool is_device_dma_coherent(struct device *dev)
 
   #include <asm-generic/dma-mapping-common.h>
 
+#ifdef CONFIG_IOMMU_DMA
+static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)
+{
+	return dev->archdata.dma_domain;
+}
+
+static inline void set_dma_domain(struct device *dev,
+				  struct iommu_dma_domain *dma_domain)
+{

arch/arm64/include/asm/dma-mapping.h static inline bool is_device_dma_coherent(struct device *dev) · line 83

Quoted 10 lines

arch/arm64/include/asm/dma-mapping.h +6 -0

+	dev->archdata.dma_domain = dma_domain;
+}
+#endif
+
   static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
   {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return DMA_ERROR_CODE;
   	return (dma_addr_t)paddr;
   }

Hi Robin,

Build fail if CONFIG_IOMMU_DMA is not enabled.

In file included from ../include/linux/dma-mapping.h:82:0,

                   from ../arch/arm64/kernel/asm-offsets.c:23:
../arch/arm64/include/asm/dma-mapping.h: In function 'phys_to_dma':
../arch/arm64/include/asm/dma-mapping.h:81:2: error: implicit declaration of function 'get_dma_domain' [-Werror=implicit-function-declaration]
    if (WARN_ON(dev && get_dma_domain(dev)))
    ^

Quoted 8 lines

Quoted 1 line

Joe.C

Bah, how did I manage to make such a half-finished mess of the includes? Current fixup diff below.

Thanks,
Robin.

Dear Robin,
We have test this patch on our mt8173, it also could work well.

Tested-by Yong Wu <[email protected]>

And I have 2 questiones about how to use this iommu. 1)if We call "arch_setup_dma_ops" to create a iommu domain, then is
this function "bus_set_iommu" who also need "struct iommu_ops *" necessary to be called or not in your design?

2)int (*domain_init)(struct iommu_domain *domain);
About this function, it will alloc pagetable for the iommu
domain. And We expect the pagetable memory is uncacheable, so try to call "dma_alloc_coherent", unfortunately the "struct device *" can't be passed into this function. so is it possible if adding a parameter in this function.

Quoted 6 lines

2)int (*domain_init)(struct iommu_domain *domain);
About this function, it will alloc pagetable for the iommu
domain. And We expect the pagetable memory is uncacheable, so try to call "dma_alloc_coherent", unfortunately the "struct device *" can't be passed into this function. so is it possible if adding a parameter in this function.

...one of the ideas of the new of_iommu_configure framework is that iommu_ops structures can represent individual IOMMU devices if necessary. The ops->priv pointer was included for that purpose, but isn't very clean so Will has plans to remove it again - it's easy enough to achieve the same effect by having the driver embed the ops in its private instance data instead. I've done that with the ARM SMMU driver which has a similar issue of needing hardware details at domain_init() time (no patches ready yet but I have an iommu/dev branch on top of the iommu/dma branch with some current work-in-progress bits)

Thanks,
Robin.

Quoted 17 lines · Robin Murphy

Quoted 6 lines

2)int (*domain_init)(struct iommu_domain *domain);
About this function, it will alloc pagetable for the iommu
domain. And We expect the pagetable memory is uncacheable, so try to call "dma_alloc_coherent", unfortunately the "struct device *" can't be passed into this function. so is it possible if adding a parameter in this function.

...one of the ideas of the new of_iommu_configure framework is that iommu_ops structures can represent individual IOMMU devices if necessary. The ops->priv pointer was included for that purpose, but isn't very clean so Will has plans to remove it again - it's easy enough to achieve the same effect by having the driver embed the ops in its private instance data instead. I've done that with the ARM SMMU driver which has a similar issue of needing hardware details at domain_init() time (no patches ready yet but I have an iommu/dev branch on top of the iommu/dma branch with some current work-in-progress bits)

Quoted 3 lines

Thanks,
Robin.

Dear Robin,
Thanks very much for your suggestion.

I have a more question: how to do cache maintenance in arm64.

a) "__dma_flush_range" can not be expected to used directly.
b) Following Documentation\DMA-API.txt, section: Streaming DMA
mappings. dma_map_single should be used, But I am not sure how to pass the first "struct device *".
We have a device which call arch_setup_dma_ops to create the
iommu domain, if we use this device, it will enter __iommu_map_page;
If we input NULL for dmap_map_single, it will assert at
dma_capable in swiotlb_map_page...

And normally, we always need do cache maintenance only for some
bytes in the pagetable but not whole a page. Then is there a easy way to do the cache maintenance?

Quoted 27 lines · Yong Wu

Quoted 17 lines · Robin Murphy

Quoted 6 lines

2)int (*domain_init)(struct iommu_domain *domain);
About this function, it will alloc pagetable for the iommu
domain. And We expect the pagetable memory is uncacheable, so try to call "dma_alloc_coherent", unfortunately the "struct device *" can't be passed into this function. so is it possible if adding a parameter in this function.

...one of the ideas of the new of_iommu_configure framework is that iommu_ops structures can represent individual IOMMU devices if necessary. The ops->priv pointer was included for that purpose, but isn't very clean so Will has plans to remove it again - it's easy enough to achieve the same effect by having the driver embed the ops in its private instance data instead. I've done that with the ARM SMMU driver which has a similar issue of needing hardware details at domain_init() time (no patches ready yet but I have an iommu/dev branch on top of the iommu/dma branch with some current work-in-progress bits)

Quoted 3 lines

Thanks,
Robin.

Dear Robin,
Thanks very much for your suggestion.

I have a more question: how to do cache maintenance in arm64.

Quoted 8 lines

a) "__dma_flush_range" can not be expected to used directly.
b) Following Documentation\DMA-API.txt, section: Streaming DMA
mappings. dma_map_single should be used, But I am not sure how to pass the first "struct device *".
We have a device which call arch_setup_dma_ops to create the
iommu domain, if we use this device, it will enter __iommu_map_page;
If we input NULL for dmap_map_single, it will assert at
dma_capable in swiotlb_map_page...

Consider that the IOMMU's page table walker is a DMA master in its own

Quoted 4 lines

And normally, we always need do cache maintenance only for some
bytes in the pagetable but not whole a page. Then is there a easy way to do the cache maintenance?

For a noncoherent device, dma_map_single() will end up calling

Robin.

Quoted 1 line

Consider that the IOMMU's page table walker is a DMA master in its own

right, and that is the device you're mapping the page tables for. Therefore your IOMMU driver needs to have access to the struct device of the IOMMU itself to use for the page-table-related mappings. Also, be sure to set the IOMMU's DMA mask correctly to prevent SWIOTLB bounce buffers being created in the process (which as I've found generally ends in disaster).

Quoted 6 lines

Quoted 4 lines

And normally, we always need do cache maintenance only for some
bytes in the pagetable but not whole a page. Then is there a easy way to do the cache maintenance?

For a noncoherent device, dma_map_single() will end up calling

__dma_map_area() with the page offset and size of the original request, so the updated part gets flushed by VA, and the rest of the page isn't touched if it doesn't need to be. On the other hand if the page tables were allocated with dma_alloc_coherent() in the first place, then just calling dma_sync_single_for_device() for the updated region should suffice.

Quoted 1 line

Where exactly would you call the dma_unmap? It seems a bit strange to be repeatedly calling dma_map and never calling dma_unmap. I don't see it explicitly forbidden in the docs anywhere to do this but it seems like it would be violating the implicit handoff of dma_map/dma_unmap.

Hi Laura,

On 05/03/15 00:19, Laura Abbott wrote:
[...]

Quoted 18 lines

Quoted 1 line

Consider that the IOMMU's page table walker is a DMA master in its own

right, and that is the device you're mapping the page tables for. Therefore your IOMMU driver needs to have access to the struct device of the IOMMU itself to use for the page-table-related mappings. Also, be sure to set the IOMMU's DMA mask correctly to prevent SWIOTLB bounce buffers being created in the process (which as I've found generally ends in disaster).

Quoted 6 lines

Quoted 4 lines

And normally, we always need do cache maintenance only for some
bytes in the pagetable but not whole a page. Then is there a easy way to do the cache maintenance?

For a noncoherent device, dma_map_single() will end up calling

__dma_map_area() with the page offset and size of the original request, so the updated part gets flushed by VA, and the rest of the page isn't touched if it doesn't need to be. On the other hand if the page tables were allocated with dma_alloc_coherent() in the first place, then just calling dma_sync_single_for_device() for the updated region should suffice.

Quoted 4 lines

Where exactly would you call the dma_unmap? It seems a bit strange to be repeatedly calling dma_map and never calling dma_unmap. I don't see it explicitly forbidden in the docs anywhere to do this but it seems like it would be violating the implicit handoff of dma_map/dma_unmap.

I think ideally you'd call dma_map_page when you first create the page table, dma_sync_single_for_device on any update, and dma_unmap_page when you tear it down, and you'd also use the appropriate DMA addresses everywhere instead of physical addresses.

Quoted 6 lines

Quoted 6 lines

Quoted 1 line

For a noncoherent device, dma_map_single() will end up calling

__dma_map_area() with the page offset and size of the original request, so the updated part gets flushed by VA, and the rest of the page isn't touched if it doesn't need to be. On the other hand if the page tables were allocated with dma_alloc_coherent() in the first place, then just calling dma_sync_single_for_device() for the updated region should suffice.

That's wrong. dma_sync_single_*() is not permitted to be called on coherently allocated memory. Where coherent memory needs to be remapped, dma_sync_single_*() will panic the kernel.

If it's in coherent memory, all you should need is the appropriate memory barrier to ensure that the DMA agent can see the writes.

Quoted 9 lines

Quoted 4 lines

Where exactly would you call the dma_unmap? It seems a bit strange to be repeatedly calling dma_map and never calling dma_unmap. I don't see it explicitly forbidden in the docs anywhere to do this but it seems like it would be violating the implicit handoff of dma_map/dma_unmap.

I think ideally you'd call dma_map_page when you first create the page table, dma_sync_single_for_device on any update, and dma_unmap_page when you tear it down, and you'd also use the appropriate DMA addresses everywhere instead of physical addresses.

No.

dma_map_page() ownership changes CPU->DMA
dma_sync_single_for_cpu() ownership changes DMA->CPU
dma_sync_single_for_device() ownership changes CPU->DMA
dma_unmap_page() ownership changes DMA->CPU

It's invalid to miss out the pairing that give those ownership changes.

Quoted 5 lines

Quoted 4 lines

I think ideally you'd call dma_map_page when you first create the page table, dma_sync_single_for_device on any update, and dma_unmap_page when you tear it down, and you'd also use the appropriate DMA addresses everywhere instead of physical addresses.

Quoted 8 lines

No.

dma_map_page() ownership changes CPU->DMA
dma_sync_single_for_cpu() ownership changes DMA->CPU
dma_sync_single_for_device() ownership changes CPU->DMA
dma_unmap_page() ownership changes DMA->CPU

It's invalid to miss out the pairing that give those ownership changes.

Thanks for the clarification - the wording in DMA-API.txt rather implies that in the DMA_TO_DEVICE case you only have to sync the updated data /after/ writing it. For the sake of purely getting pages flushed, would it be more reasonable then to call dma_map_single() followed immediately by dma_unmap_single_attrs() with DMA_ATTR_SKIP_CPU_SYNC? Since we know the IOMMU can never write back to memory (ones that can are a different issue) it would be nice to be able to skip the extra invalidations somehow, without too heinously abusing the API.

Robin.

_______________________________________________
iommu mailing list
iommu at lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

Taking some inspiration from the arch/arm code, implement the arch-specific side of the DMA mapping ops using the new IOMMU-DMA layer.

Signed-off-by Robin Murphy <[email protected]>

---
  arch/arm64/include/asm/device.h      |   3 +
  arch/arm64/include/asm/dma-mapping.h |  17 ++
  arch/arm64/mm/dma-mapping.c          | 320 +++++++++++++++++++++++++++++++++++
  3 files changed, 340 insertions(+)

arch/arm64/include/asm/device.h +3 -0

index 243ef25..510cee1 100644
@@ -20,6 +20,9 @@ struct dev_archdata {
  	struct dma_map_ops *dma_ops;
  #ifdef CONFIG_IOMMU_API
  	void *iommu;			/* private IOMMU data */
+#ifdef CONFIG_IOMMU_DMA
+	struct iommu_dma_domain *dma_domain;
+#endif
  #endif
  	bool dma_coherent;
  };

arch/arm64/include/asm/dma-mapping.h +17 -0

index 6932bb5..c1b271f 100644
@@ -62,13 +62,30 @@ static inline bool is_device_dma_coherent(struct device *dev)
 
  #include <asm-generic/dma-mapping-common.h>
 
+#ifdef CONFIG_IOMMU_DMA
+static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)
+{
+	return dev->archdata.dma_domain;
+}
+
+static inline void set_dma_domain(struct device *dev,
+				  struct iommu_dma_domain *dma_domain)
+{
+	dev->archdata.dma_domain = dma_domain;
+}
+#endif
+
  static inline dma_addr_t phys_to_dma(struct device *dev, phys_addr_t paddr)
  {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return DMA_ERROR_CODE;
  	return (dma_addr_t)paddr;
  }
 
  static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t dev_addr)
  {
+	if (WARN_ON(dev && get_dma_domain(dev)))
+		return 0;
  	return (phys_addr_t)dev_addr;
  }
 

arch/arm64/mm/dma-mapping.c +262 -0

index 0a24b9b..28e771c 100644
@@ -23,6 +23,7 @@
  #include <linux/genalloc.h>
  #include <linux/dma-mapping.h>
  #include <linux/dma-contiguous.h>
+#include <linux/dma-iommu.h>
  #include <linux/vmalloc.h>
  #include <linux/swiotlb.h>
 

@@ -426,6 +427,7 @@ static int __init arm64_dma_init(void)
 
  	ret |= swiotlb_late_init();
  	ret |= atomic_pool_init();
+	ret |= iommu_dma_init();
 
  	return ret;
  }

@@ -439,3 +441,321 @@ static int __init dma_debug_do_init(void)
  	return 0;
  }
  fs_initcall(dma_debug_do_init);
+
+
+#ifdef CONFIG_IOMMU_DMA
+
+static struct page **__atomic_get_pages(void *addr)
+{
+	struct page *page;
+	phys_addr_t phys;
+
+	phys = gen_pool_virt_to_phys(atomic_pool, (unsigned long)addr);
+	page = phys_to_page(phys);
+
+	return (struct page **)page;
+}
+
+static struct page **__iommu_get_pages(void *cpu_addr, struct dma_attrs *attrs)
+{
+	struct vm_struct *area;
+
+	if (__in_atomic_pool(cpu_addr, PAGE_SIZE))
+		return __atomic_get_pages(cpu_addr);
+
+	area = find_vm_area(cpu_addr);
+	if (!area)
+		return NULL;
+
+	return area->pages;
+}
+
+static void *__iommu_alloc_atomic(struct device *dev, size_t size,
+				  dma_addr_t *handle, bool coherent)
+{
+	struct page *page;
+	void *addr;
+
+	addr = __alloc_from_pool(size, &page);
+	if (!addr)
+		return NULL;
+
+	*handle = iommu_dma_create_iova_mapping(dev, &page, size, coherent);
+	if (*handle == DMA_ERROR_CODE) {
+		__free_from_pool(addr, size);
+		return NULL;
+	}
+	return addr;
+}
+
+static void __iommu_free_atomic(struct device *dev, void *cpu_addr,
+				dma_addr_t handle, size_t size)
+{
+	iommu_dma_release_iova_mapping(dev, handle, size);
+	__free_from_pool(cpu_addr, size);
+}
+
+static void __dma_clear_buffer(struct page *page, size_t size)
+{
+	void *ptr = page_address(page);
+
+	memset(ptr, 0, size);
+	__dma_flush_range(ptr, ptr + size);
+}
+
+static void *__iommu_alloc_attrs(struct device *dev, size_t size,
+				 dma_addr_t *handle, gfp_t gfp,
+				 struct dma_attrs *attrs)
+{
+	bool coherent = is_device_dma_coherent(dev);
+	pgprot_t prot = coherent ? __pgprot(PROT_NORMAL) :
+				   __pgprot(PROT_NORMAL_NC);
+	struct page **pages;
+	void *addr = NULL;
+
+	*handle = DMA_ERROR_CODE;
+	size = PAGE_ALIGN(size);
+
+	if (!(gfp & __GFP_WAIT))
+		return __iommu_alloc_atomic(dev, size, handle, coherent);
+	/*
+	 * FIXME: This isn't even true any more!
+	 *
+	 * Following is a work-around (a.k.a. hack) to prevent pages
+	 * with __GFP_COMP being passed to split_page() which cannot
+	 * handle them.  The real problem is that this flag probably
+	 * should be 0 on ARM as it is not supported on this
+	 * platform; see CONFIG_HUGETLBFS.
+	 */
+	gfp &= ~(__GFP_COMP);
+
+	pages = iommu_dma_alloc_buffer(dev, size, gfp, attrs,
+			__dma_clear_buffer);
+	if (!pages)
+		return NULL;
+
+	*handle = iommu_dma_create_iova_mapping(dev, pages, size, coherent);
+	if (*handle == DMA_ERROR_CODE)
+		goto err_mapping;
+
+	addr = dma_common_pages_remap(pages, size, VM_USERMAP,
+				      __get_dma_pgprot(attrs, prot, coherent),
+				      __builtin_return_address(0));
+	if (addr)
+		return addr;
+
+	iommu_dma_release_iova_mapping(dev, *handle, size);
+err_mapping:
+	iommu_dma_free_buffer(dev, pages, size, attrs);
+	return NULL;
+}
+
+static void __iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
+			       dma_addr_t handle, struct dma_attrs *attrs)
+{
+	struct page **pages;
+
+	size = PAGE_ALIGN(size);
+	if (__in_atomic_pool(cpu_addr, size)) {
+		__iommu_free_atomic(dev, cpu_addr, handle, size);
+		return;
+	}
+
+	pages = __iommu_get_pages(cpu_addr, attrs);
+	if (!pages) {
+		WARN(1, "trying to free invalid coherent area: %p\n", cpu_addr);
+		return;
+	}
+
+	dma_common_free_remap(cpu_addr, size, VM_USERMAP);
+
+	iommu_dma_release_iova_mapping(dev, handle, size);
+	iommu_dma_free_buffer(dev, pages, size, attrs);
+}
+
+static int __iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
+			      void *cpu_addr, dma_addr_t dma_addr, size_t size,
+			      struct dma_attrs *attrs)
+{
+	unsigned long uaddr = vma->vm_start;
+	unsigned long usize = vma->vm_end - vma->vm_start;
+	struct page **pages = __iommu_get_pages(cpu_addr, attrs);
+	int ret;
+
+	if (!pages)
+		return -ENXIO;
+
+	vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot,
+					     is_device_dma_coherent(dev));
+
+	if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
+		return ret;
+
+	do {
+		ret = vm_insert_page(vma, uaddr, *pages++);
+		if (ret) {
+			pr_err("Remapping memory failed: %d\n", ret);
+			return ret;
+		}
+		uaddr += PAGE_SIZE;
+		usize -= PAGE_SIZE;
+	} while (usize > 0);
+
+	return 0;
+}
+
+static void __iommu_sync_single_for_cpu(struct device *dev,
+					dma_addr_t dev_addr, size_t size,
+					enum dma_data_direction dir)
+{
+	if (!is_device_dma_coherent(dev) && (dev_addr != DMA_ERROR_CODE)) {
+		struct iommu_dma_domain *dma_domain = get_dma_domain(dev);
+		struct iommu_domain *domain = iommu_dma_raw_domain(dma_domain);
+		phys_addr_t phys = iommu_iova_to_phys(domain, dev_addr);
+
+		__dma_unmap_area(phys_to_virt(phys), size, dir);
+	}
+}
+
+static void __iommu_sync_single_for_device(struct device *dev,
+					   dma_addr_t dev_addr, size_t size,
+					   enum dma_data_direction dir)
+{
+	if (!is_device_dma_coherent(dev) && (dev_addr != DMA_ERROR_CODE)) {
+		struct iommu_dma_domain *dma_domain = get_dma_domain(dev);
+		struct iommu_domain *domain = iommu_dma_raw_domain(dma_domain);
+		phys_addr_t phys = iommu_iova_to_phys(domain, dev_addr);
+
+		__dma_map_area(phys_to_virt(phys), size, dir);
+	}
+}
+
+static dma_addr_t __iommu_map_page(struct device *dev, struct page *page,
+				   unsigned long offset, size_t size,
+				   enum dma_data_direction dir,
+				   struct dma_attrs *attrs)
+{
+	dma_addr_t dev_addr;
+
+	if (is_device_dma_coherent(dev))
+		return iommu_dma_coherent_map_page(dev, page, offset, size,
+				dir, attrs);
+
+	dev_addr = iommu_dma_map_page(dev, page, offset, size, dir, attrs);
+
+	if (!dma_get_attr(DMA_ATTR_SKIP_CPU_SYNC, attrs))
+		__iommu_sync_single_for_device(dev, dev_addr, size, dir);
+
+	return dev_addr;
+}
+
+static void __iommu_unmap_page(struct device *dev, dma_addr_t dev_addr,
+			       size_t size, enum dma_data_direction dir,
+			       struct dma_attrs *attrs)
+{
+	if (!dma_get_attr(DMA_ATTR_SKIP_CPU_SYNC, attrs))
+		__iommu_sync_single_for_cpu(dev, dev_addr, size, dir);
+
+	iommu_dma_unmap_page(dev, dev_addr, size, dir, attrs);
+}
+
+static void __iommu_sync_sg_for_cpu(struct device *dev,
+				    struct scatterlist *sgl, int nelems,
+				    enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	if (is_device_dma_coherent(dev))
+		return;
+
+	for_each_sg(sgl, sg, nelems, i)
+		__dma_unmap_area(sg_virt(sg), sg->length, dir);
+}
+
+static void __iommu_sync_sg_for_device(struct device *dev,
+				       struct scatterlist *sgl, int nelems,
+				       enum dma_data_direction dir)
+{
+	struct scatterlist *sg;
+	int i;
+
+	if (is_device_dma_coherent(dev))
+		return;
+
+	for_each_sg(sgl, sg, nelems, i)
+		__dma_map_area(sg_virt(sg), sg->length, dir);
+}
+
+static int __iommu_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
+				int nelems, enum dma_data_direction dir,
+				struct dma_attrs *attrs)
+{
+	if (is_device_dma_coherent(dev))
+		return iommu_dma_coherent_map_sg(dev, sgl, nelems, dir, attrs);
+
+	if (!dma_get_attr(DMA_ATTR_SKIP_CPU_SYNC, attrs))
+		__iommu_sync_sg_for_device(dev, sgl, nelems, dir);
+
+	return iommu_dma_map_sg(dev, sgl, nelems, dir, attrs);
+}
+
+static void __iommu_unmap_sg_attrs(struct device *dev,

arch/arm64/mm/dma-mapping.c +38 -0

+static struct dma_map_ops iommu_dma_ops = {
+	.alloc = __iommu_alloc_attrs,
+	.free = __iommu_free_attrs,
+	.mmap = __iommu_mmap_attrs,
+	.map_page = __iommu_map_page,
+	.unmap_page = __iommu_unmap_page,
+	.map_sg = __iommu_map_sg_attrs,
+	.unmap_sg = __iommu_unmap_sg_attrs,
+	.sync_single_for_cpu = __iommu_sync_single_for_cpu,
+	.sync_single_for_device = __iommu_sync_single_for_device,
+	.sync_sg_for_cpu = __iommu_sync_sg_for_cpu,
+	.sync_sg_for_device = __iommu_sync_sg_for_device,
+	.dma_supported = iommu_dma_supported,
+	.mapping_error = iommu_dma_mapping_error,
+};
+
+static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+				  const struct iommu_ops *ops)
+{
+	struct iommu_dma_domain *dma_domain;
+
+	if (!ops)
+		return;
+
+	dma_domain = iommu_dma_create_domain(ops, dma_base, size);
+	if (!dma_domain) {
+		pr_warn("Failed to create %llu-byte IOMMU mapping for device %s\n",
+				size, dev_name(dev));
+		return;
+	}
+
+	if (iommu_dma_attach_device(dev, dma_domain))
+		pr_warn("Failed to attach device %s to IOMMU mapping\n",
+				dev_name(dev));
+	else
+		dev->archdata.dma_ops = &iommu_dma_ops;
+
+	/* drop the initial mapping refcount */

With iommu_dma_ops in place, hook them up to the configuration code, so IOMMU-fronted devices will get them automatically.

Signed-off-by Robin Murphy <[email protected]>

---
 arch/arm64/Kconfig                   |  1 +
 arch/arm64/include/asm/dma-mapping.h | 11 ++++++-----
 arch/arm64/mm/dma-mapping.c          | 15 +++++++++++++++
 3 files changed, 22 insertions(+), 5 deletions(-)

arch/arm64/Kconfig +0 -0

index b1f9a20..e2abcdc 100644

arch/arm64/Kconfig +0 -0

 	select IRQ_DOMAIN
 	select MODULES_USE_ELF_RELA
 	select NO_BOOTMEM

arch/arm64/include/asm/dma-mapping.h +6 -5

index c1b271f..5246d1a 100644
@@ -45,11 +45,8 @@ static inline struct dma_map_ops *get_dma_ops(struct device *dev)
 		return __generic_dma_ops(dev);
 }
 
-static inline void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
-				      struct iommu_ops *iommu, bool coherent)
-{
-	dev->archdata.dma_coherent = coherent;
-}
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+			struct iommu_ops *iommu, bool coherent);
 #define arch_setup_dma_ops	arch_setup_dma_ops
 
 /* do not use this function in a driver */

@@ -63,6 +60,10 @@ static inline bool is_device_dma_coherent(struct device *dev)
 #include <asm-generic/dma-mapping-common.h>
 
 #ifdef CONFIG_IOMMU_DMA
+
+void arch_teardown_dma_ops(struct device *dev);
+#define arch_teardown_dma_ops	arch_teardown_dma_ops
+
 static inline struct iommu_dma_domain *get_dma_domain(struct device *dev)
 {
 	return dev->archdata.dma_domain;

arch/arm64/mm/dma-mapping.c +15 -0

index 28e771c..2a30673 100644
@@ -752,6 +752,14 @@ static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 	iommu_dma_release_domain(dma_domain);
 }
 
+void arch_teardown_dma_ops(struct device *dev)
+{
+	if (dev->archdata.dma_domain) {
+		iommu_dma_detach_device(dev);
+		dev->archdata.dma_ops = NULL;
+	}
+}
+
 #else
 
 static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,

@@ -759,3 +767,10 @@ static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 { }
 
 #endif  /* CONFIG_IOMMU_DMA */
+
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+			struct iommu_ops *iommu, bool coherent)
+{
+	dev->archdata.dma_coherent = coherent;
+	__iommu_setup_dma_ops(dev, dma_base, size, iommu);
+}

Quoted 10 lines · Robin Murphy

With iommu_dma_ops in place, hook them up to the configuration code, so IOMMU-fronted devices will get them automatically.

Signed-off-by Robin Murphy <[email protected]>

---
  arch/arm64/Kconfig                   |  1 +
  arch/arm64/include/asm/dma-mapping.h | 11 ++++++-----
  arch/arm64/mm/dma-mapping.c          | 15 +++++++++++++++
  3 files changed, 22 insertions(+), 5 deletions(-)

arch/arm64/Kconfig config ARM64 · line 69

Quoted 9 lines

arch/arm64/Kconfig +1 -0

index b1f9a20..e2abcdc 100644
@@ -66,6 +66,7 @@ config ARM64
  	select HAVE_PERF_USER_STACK_DUMP
  	select HAVE_RCU_TABLE_FREE
  	select HAVE_SYSCALL_TRACEPOINTS
+	select IOMMU_DMA if IOMMU_SUPPORT

IOMMU_SUPPORT is selected above, so "if IOMMU_SUPPORT" can be omitted. And I suggest putting "select IOMMU_DMA" next to "select IOMMU_SUPPORT".