avoid indirect calls for DMA direct mappings v2

Instead of providing a special dma_mark_clean hook just for ia64, switch ia64 to use the normal arch_sync_dma_for_cpu hooks instead.

This means that we now also set the PG_arch_1 bit for pages in the swiotlb buffer, which isn't stricly needed as we will never execute code out of the swiotlb buffer, but otherwise harmless.

Quoted 7 lines · Christoph Hellwig

Instead of providing a special dma_mark_clean hook just for ia64, switch ia64 to use the normal arch_sync_dma_for_cpu hooks instead.

This means that we now also set the PG_arch_1 bit for pages in the swiotlb buffer, which isn't stricly needed as we will never execute code out of the swiotlb buffer, but otherwise harmless.

ia64 build based on arch/ia64/configs/zx1_defconfig now fails with undefined symbols arch_dma_alloc and arch_dma_free (used by kernel/dma/direct.c).

This config doesn't define CONFIG_SWIOTLB, so we don't get the benefit of the routines in arch/ia64/kernel/dma-mapping.c

From: Robin Murphy <[email protected]>

Rather than checking the DMA attribute at each callsite, just pass it through for acpi_dma_configure() to handle directly. That can then deal with the relatively exceptional DEV_DMA_NOT_SUPPORTED case by explicitly installing dummy DMA ops instead of just skipping setup entirely. This will then free up the dev->dma_ops = NULL case for some valuable fastpath optimisations.

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

Signed-off-by Christoph Hellwig <[email protected]>

---
 drivers/acpi/scan.c      | 5 +++++
 drivers/base/platform.c  | 3 +--
 drivers/pci/pci-driver.c | 3 +--

 3 files changed, 7 insertions(+), 4 deletions(-)

drivers/acpi/scan.c +5 -0

index bd1c59fb0e17..b75ae34ed188 100644
@@ -1456,6 +1456,11 @@ int acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
 	const struct iommu_ops *iommu;
 	u64 dma_addr = 0, size = 0;
 
+	if (attr = DEV_DMA_NOT_SUPPORTED) {
+		set_dma_ops(dev, &dma_dummy_ops);
+		return 0;
+	}
+
 	iort_dma_setup(dev, &dma_addr, &size);
 
 	iommu = iort_iommu_configure(dev);

drivers/base/platform.c +1 -2

index eae841935a45..c1ddf191711e 100644
@@ -1138,8 +1138,7 @@ int platform_dma_configure(struct device *dev)
 		ret = of_dma_configure(dev, dev->of_node, true);
 	} else if (has_acpi_companion(dev)) {
 		attr = acpi_get_dma_attr(to_acpi_device_node(dev->fwnode));
-		if (attr != DEV_DMA_NOT_SUPPORTED)
-			ret = acpi_dma_configure(dev, attr);
+		ret = acpi_dma_configure(dev, attr);
 	}
 
 	return ret;

drivers/pci/pci-driver.c +1 -2

index bef17c3fca67..1b58e058b13f 100644
@@ -1602,8 +1602,7 @@ static int pci_dma_configure(struct device *dev)
 		struct acpi_device *adev = to_acpi_device_node(bridge->fwnode);
 		enum dev_dma_attr attr = acpi_get_dma_attr(adev);
 
-		if (attr != DEV_DMA_NOT_SUPPORTED)
-			ret = acpi_dma_configure(dev, attr);
+		ret = acpi_dma_configure(dev, acpi_get_dma_attr(adev));
 	}
 
 	pci_put_host_bridge_device(bridge);

Signature · 1 line

2.19.1

With the bypass support for the direct mapping we might not always have methods to call, so use the proper APIs instead. The only downside is that we will create two dma-debug entries for each mapping if CONFIG_DMA_DEBUG is enabled.

Signed-off-by Christoph Hellwig <[email protected]>

---
 drivers/pci/controller/vmd.c | 42 +++++++++++++++---------------------
 1 file changed, 17 insertions(+), 25 deletions(-)

drivers/pci/controller/vmd.c +17 -25

index 98ce79eac128..3890812cdf87 100644
@@ -307,39 +307,32 @@ static struct device *to_vmd_dev(struct device *dev)
 	return &vmd->dev->dev;
 }
 
-static const struct dma_map_ops *vmd_dma_ops(struct device *dev)
-{
-	return get_dma_ops(to_vmd_dev(dev));
-}
-
 static void *vmd_alloc(struct device *dev, size_t size, dma_addr_t *addr,
 		       gfp_t flag, unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->alloc(to_vmd_dev(dev), size, addr, flag,
-				       attrs);
+	return dma_alloc_attrs(to_vmd_dev(dev), size, addr, flag, attrs);
 }
 
 static void vmd_free(struct device *dev, size_t size, void *vaddr,
 		     dma_addr_t addr, unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->free(to_vmd_dev(dev), size, vaddr, addr,
-				      attrs);
+	return dma_free_attrs(to_vmd_dev(dev), size, vaddr, addr, attrs);
 }
 
 static int vmd_mmap(struct device *dev, struct vm_area_struct *vma,
 		    void *cpu_addr, dma_addr_t addr, size_t size,
 		    unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->mmap(to_vmd_dev(dev), vma, cpu_addr, addr,
-				      size, attrs);
+	return dma_mmap_attrs(to_vmd_dev(dev), vma, cpu_addr, addr, size,
+			attrs);
 }
 
 static int vmd_get_sgtable(struct device *dev, struct sg_table *sgt,
 			   void *cpu_addr, dma_addr_t addr, size_t size,
 			   unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->get_sgtable(to_vmd_dev(dev), sgt, cpu_addr,
-					     addr, size, attrs);
+	return dma_get_sgtable_attrs(to_vmd_dev(dev), sgt, cpu_addr, addr, size,
+			attrs);
 }
 
 static dma_addr_t vmd_map_page(struct device *dev, struct page *page,

@@ -347,61 +340,60 @@ static dma_addr_t vmd_map_page(struct device *dev, struct page *page,
 			       enum dma_data_direction dir,
 			       unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->map_page(to_vmd_dev(dev), page, offset, size,
-					  dir, attrs);
+	return dma_map_page_attrs(to_vmd_dev(dev), page, offset, size, dir,
+			attrs);
 }
 
 static void vmd_unmap_page(struct device *dev, dma_addr_t addr, size_t size,
 			   enum dma_data_direction dir, unsigned long attrs)
 {
-	vmd_dma_ops(dev)->unmap_page(to_vmd_dev(dev), addr, size, dir, attrs);
+	dma_unmap_page_attrs(to_vmd_dev(dev), addr, size, dir, attrs);
 }
 
 static int vmd_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 		      enum dma_data_direction dir, unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->map_sg(to_vmd_dev(dev), sg, nents, dir, attrs);
+	return dma_map_sg_attrs(to_vmd_dev(dev), sg, nents, dir, attrs);
 }
 
 static void vmd_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 			 enum dma_data_direction dir, unsigned long attrs)
 {
-	vmd_dma_ops(dev)->unmap_sg(to_vmd_dev(dev), sg, nents, dir, attrs);
+	dma_unmap_sg_attrs(to_vmd_dev(dev), sg, nents, dir, attrs);
 }
 
 static void vmd_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
 				    size_t size, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_single_for_cpu(to_vmd_dev(dev), addr, size, dir);
+	dma_sync_single_for_cpu(to_vmd_dev(dev), addr, size, dir);
 }
 
 static void vmd_sync_single_for_device(struct device *dev, dma_addr_t addr,
 				       size_t size, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_single_for_device(to_vmd_dev(dev), addr, size,
-						 dir);
+	dma_sync_single_for_device(to_vmd_dev(dev), addr, size, dir);
 }
 
 static void vmd_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
 				int nents, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_sg_for_cpu(to_vmd_dev(dev), sg, nents, dir);
+	dma_sync_sg_for_cpu(to_vmd_dev(dev), sg, nents, dir);
 }
 
 static void vmd_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 				   int nents, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_sg_for_device(to_vmd_dev(dev), sg, nents, dir);
+	dma_sync_sg_for_device(to_vmd_dev(dev), sg, nents, dir);
 }
 
 static int vmd_dma_supported(struct device *dev, u64 mask)
 {
-	return vmd_dma_ops(dev)->dma_supported(to_vmd_dev(dev), mask);
+	return dma_supported(to_vmd_dev(dev), mask);
 }
 
 static u64 vmd_get_required_mask(struct device *dev)
 {
-	return vmd_dma_ops(dev)->get_required_mask(to_vmd_dev(dev));
+	return dma_get_required_mask(to_vmd_dev(dev));
 }
 
 static void vmd_teardown_dma_ops(struct vmd_dev *vmd)

Signature · 1 line

2.19.1

Conventional spelling in subject is

PCI: vmd: Use dma_* APIs instead of direct method calls

Quoted 6 lines · Christoph Hellwig

With the bypass support for the direct mapping we might not always have methods to call, so use the proper APIs instead. The only downside is that we will create two dma-debug entries for each mapping if CONFIG_DMA_DEBUG is enabled.

Signed-off-by Christoph Hellwig <[email protected]>

You cc'd the VMD maintainers already, and I have no objection to this from a PCI core point of view, so:

Acked-by Bjorn Helgaas <[email protected]>

Quoted 130 lines

---
 drivers/pci/controller/vmd.c | 42 +++++++++++++++---------------------
 1 file changed, 17 insertions(+), 25 deletions(-)

drivers/pci/controller/vmd.c +17 -25

index 98ce79eac128..3890812cdf87 100644
@@ -307,39 +307,32 @@ static struct device *to_vmd_dev(struct device *dev)
 	return &vmd->dev->dev;
 }
 
-static const struct dma_map_ops *vmd_dma_ops(struct device *dev)
-{
-	return get_dma_ops(to_vmd_dev(dev));
-}
-
 static void *vmd_alloc(struct device *dev, size_t size, dma_addr_t *addr,
 		       gfp_t flag, unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->alloc(to_vmd_dev(dev), size, addr, flag,
-				       attrs);
+	return dma_alloc_attrs(to_vmd_dev(dev), size, addr, flag, attrs);
 }
 
 static void vmd_free(struct device *dev, size_t size, void *vaddr,
 		     dma_addr_t addr, unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->free(to_vmd_dev(dev), size, vaddr, addr,
-				      attrs);
+	return dma_free_attrs(to_vmd_dev(dev), size, vaddr, addr, attrs);
 }
 
 static int vmd_mmap(struct device *dev, struct vm_area_struct *vma,
 		    void *cpu_addr, dma_addr_t addr, size_t size,
 		    unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->mmap(to_vmd_dev(dev), vma, cpu_addr, addr,
-				      size, attrs);
+	return dma_mmap_attrs(to_vmd_dev(dev), vma, cpu_addr, addr, size,
+			attrs);
 }
 
 static int vmd_get_sgtable(struct device *dev, struct sg_table *sgt,
 			   void *cpu_addr, dma_addr_t addr, size_t size,
 			   unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->get_sgtable(to_vmd_dev(dev), sgt, cpu_addr,
-					     addr, size, attrs);
+	return dma_get_sgtable_attrs(to_vmd_dev(dev), sgt, cpu_addr, addr, size,
+			attrs);
 }
 
 static dma_addr_t vmd_map_page(struct device *dev, struct page *page,

@@ -347,61 +340,60 @@ static dma_addr_t vmd_map_page(struct device *dev, struct page *page,
 			       enum dma_data_direction dir,
 			       unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->map_page(to_vmd_dev(dev), page, offset, size,
-					  dir, attrs);
+	return dma_map_page_attrs(to_vmd_dev(dev), page, offset, size, dir,
+			attrs);
 }
 
 static void vmd_unmap_page(struct device *dev, dma_addr_t addr, size_t size,
 			   enum dma_data_direction dir, unsigned long attrs)
 {
-	vmd_dma_ops(dev)->unmap_page(to_vmd_dev(dev), addr, size, dir, attrs);
+	dma_unmap_page_attrs(to_vmd_dev(dev), addr, size, dir, attrs);
 }
 
 static int vmd_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 		      enum dma_data_direction dir, unsigned long attrs)
 {
-	return vmd_dma_ops(dev)->map_sg(to_vmd_dev(dev), sg, nents, dir, attrs);
+	return dma_map_sg_attrs(to_vmd_dev(dev), sg, nents, dir, attrs);
 }
 
 static void vmd_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 			 enum dma_data_direction dir, unsigned long attrs)
 {
-	vmd_dma_ops(dev)->unmap_sg(to_vmd_dev(dev), sg, nents, dir, attrs);
+	dma_unmap_sg_attrs(to_vmd_dev(dev), sg, nents, dir, attrs);
 }
 
 static void vmd_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
 				    size_t size, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_single_for_cpu(to_vmd_dev(dev), addr, size, dir);
+	dma_sync_single_for_cpu(to_vmd_dev(dev), addr, size, dir);
 }
 
 static void vmd_sync_single_for_device(struct device *dev, dma_addr_t addr,
 				       size_t size, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_single_for_device(to_vmd_dev(dev), addr, size,
-						 dir);
+	dma_sync_single_for_device(to_vmd_dev(dev), addr, size, dir);
 }
 
 static void vmd_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
 				int nents, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_sg_for_cpu(to_vmd_dev(dev), sg, nents, dir);
+	dma_sync_sg_for_cpu(to_vmd_dev(dev), sg, nents, dir);
 }
 
 static void vmd_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 				   int nents, enum dma_data_direction dir)
 {
-	vmd_dma_ops(dev)->sync_sg_for_device(to_vmd_dev(dev), sg, nents, dir);
+	dma_sync_sg_for_device(to_vmd_dev(dev), sg, nents, dir);
 }
 
 static int vmd_dma_supported(struct device *dev, u64 mask)
 {
-	return vmd_dma_ops(dev)->dma_supported(to_vmd_dev(dev), mask);
+	return dma_supported(to_vmd_dev(dev), mask);
 }
 
 static u64 vmd_get_required_mask(struct device *dev)
 {
-	return vmd_dma_ops(dev)->get_required_mask(to_vmd_dev(dev));
+	return dma_get_required_mask(to_vmd_dev(dev));
 }
 
 static void vmd_teardown_dma_ops(struct vmd_dev *vmd)

Signature · 1 line

2.19.1

Avoid expensive indirect calls in the fast path DMA mapping operations by directly calling the dma_direct_* ops if we are using the directly mapped DMA operations.

Signed-off-by Christoph Hellwig <[email protected]>

---
 arch/alpha/include/asm/dma-mapping.h |   2 +-
 arch/arc/mm/cache.c                  |   2 +-
 arch/arm/include/asm/dma-mapping.h   |   2 +-
 arch/arm/mm/dma-mapping-nommu.c      |  14 +---
 arch/arm64/mm/dma-mapping.c          |   3 -
 arch/ia64/hp/common/hwsw_iommu.c     |   2 +-
 arch/ia64/hp/common/sba_iommu.c      |   4 +-
 arch/ia64/kernel/dma-mapping.c       |   1 -
 arch/mips/include/asm/dma-mapping.h  |   2 +-
 arch/parisc/kernel/setup.c           |   4 -
 arch/sparc/include/asm/dma-mapping.h |   4 +-
 arch/x86/kernel/pci-dma.c            |   2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c  |   2 +-
 drivers/iommu/amd_iommu.c            |  13 +---
 include/asm-generic/dma-mapping.h    |   2 +-
 include/linux/dma-direct.h           |  17 ----
 include/linux/dma-mapping.h          | 111 +++++++++++++++++++++++----
 include/linux/dma-noncoherent.h      |   5 +-
 kernel/dma/direct.c                  |  37 ++-------
 kernel/dma/mapping.c                 |  40 ++++++----
 20 files changed, 150 insertions(+), 119 deletions(-)

arch/alpha/include/asm/dma-mapping.h +1 -1

index 8beeafd4f68e..0ee6a5c99b16 100644
@@ -7,7 +7,7 @@ extern const struct dma_map_ops alpha_pci_ops;
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
 #ifdef CONFIG_ALPHA_JENSEN
-	return &dma_direct_ops;
+	return NULL;
 #else
 	return &alpha_pci_ops;
 #endif

arch/arc/mm/cache.c +1 -1

index f2701c13a66b..e188bb3ede53 100644
@@ -1280,7 +1280,7 @@ void __init arc_cache_init_master(void)
 	/*
 	 * In case of IOC (say IOC+SLC case), pointers above could still be set
 	 * but end up not being relevant as the first function in chain is not
-	 * called at all for @dma_direct_ops
+	 * called at all for devices using coherent DMA.
 	 *     arch_sync_dma_for_cpu() -> dma_cache_*() -> __dma_cache_*()
 	 */
 }

arch/arm/include/asm/dma-mapping.h +1 -1

index 965b7c846ecb..31d3b96f0f4b 100644
@@ -18,7 +18,7 @@ extern const struct dma_map_ops arm_coherent_dma_ops;
 
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
-	return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_direct_ops;
+	return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : NULL;
 }
 
 #ifdef __arch_page_to_dma

arch/arm/mm/dma-mapping-nommu.c +3 -11

index 712416ecd8e6..f304b10e23a4 100644
@@ -22,7 +22,7 @@
 #include "dma.h"
 
 /*
- *  dma_direct_ops is used if
+ *  The generic direct mapping code is used if
  *   - MMU/MPU is off
  *   - cpu is v7m w/o cache support
  *   - device is coherent

@@ -209,16 +209,9 @@ const struct dma_map_ops arm_nommu_dma_ops = {
 };
 EXPORT_SYMBOL(arm_nommu_dma_ops);
 
-static const struct dma_map_ops *arm_nommu_get_dma_map_ops(bool coherent)
-{
-	return coherent ? &dma_direct_ops : &arm_nommu_dma_ops;
-}
-
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			const struct iommu_ops *iommu, bool coherent)
 {
-	const struct dma_map_ops *dma_ops;
-
 	if (IS_ENABLED(CONFIG_CPU_V7M)) {
 		/*
 		 * Cache support for v7m is optional, so can be treated as

@@ -234,7 +227,6 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 		dev->archdata.dma_coherent = (get_cr() & CR_M) ? coherent : true;
 	}
 
-	dma_ops = arm_nommu_get_dma_map_ops(dev->archdata.dma_coherent);
-
-	set_dma_ops(dev, dma_ops);
+	if (!dev->archdata.dma_coherent)
+		set_dma_ops(dev, &arm_nommu_dma_ops);
 }

arch/arm64/mm/dma-mapping.c +0 -3

index ab1e417204d0..95eda81e3f2d 100644
@@ -462,9 +462,6 @@ static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			const struct iommu_ops *iommu, bool coherent)
 {
-	if (!dev->dma_ops)
-		dev->dma_ops = &dma_direct_ops;
-
 	dev->dma_coherent = coherent;
 	__iommu_setup_dma_ops(dev, dma_base, size, iommu);
 

arch/ia64/hp/common/hwsw_iommu.c +1 -1

index f40ca499b246..8840ed97712f 100644
@@ -38,7 +38,7 @@ static inline int use_swiotlb(struct device *dev)
 const struct dma_map_ops *hwsw_dma_get_ops(struct device *dev)
 {
 	if (use_swiotlb(dev))
-		return &dma_direct_ops;
+		return NULL;
 	return &sba_dma_ops;
 }
 EXPORT_SYMBOL(hwsw_dma_get_ops);

arch/ia64/hp/common/sba_iommu.c +2 -2

index 5ee74820a0f6..5a361e51cb1e 100644
@@ -2078,7 +2078,7 @@ sba_init(void)
 	 * a successful kdump kernel boot is to use the swiotlb.
 	 */
 	if (is_kdump_kernel()) {
-		dma_ops = &dma_direct_ops;
+		dma_ops = NULL;
 		if (swiotlb_late_init_with_default_size(64 * (1<<20)) != 0)
 			panic("Unable to initialize software I/O TLB:"
 				  " Try machvec=dig boot option");

@@ -2100,7 +2100,7 @@ sba_init(void)
 		 * If we didn't find something sba_iommu can claim, we
 		 * need to setup the swiotlb and switch to the dig machvec.
 		 */
-		dma_ops = &dma_direct_ops;
+		dma_ops = NULL;
 		if (swiotlb_late_init_with_default_size(64 * (1<<20)) != 0)
 			panic("Unable to find SBA IOMMU or initialize "
 			      "software I/O TLB: Try machvec=dig boot option");

arch/ia64/kernel/dma-mapping.c +0 -1

index 80cd3e1ea95a..ad7d9963de34 100644
@@ -36,7 +36,6 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
 
 void __init swiotlb_dma_init(void)
 {
-	dma_ops = &dma_direct_ops;
 	swiotlb_init(1);
 }
 #endif

arch/mips/include/asm/dma-mapping.h +1 -1

index 69f914667f3e..20dfaad3a55d 100644
@@ -11,7 +11,7 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 #if defined(CONFIG_MACH_JAZZ)
 	return &jazz_dma_ops;
 #else
-	return &dma_direct_ops;
+	return NULL;
 #endif
 }
 

arch/parisc/kernel/setup.c +0 -4

index cd227f1cf629..54818cd78bd0 100644
@@ -99,10 +99,6 @@ void __init dma_ops_init(void)
 
 	case pcxl2:
 		pa7300lc_init();
-	case pcxl: /* falls through */
-	case pcxs:
-	case pcxt:
-		hppa_dma_ops = &dma_direct_ops;
 		break;
 	default:
 		break;

arch/sparc/include/asm/dma-mapping.h +2 -2

index b0bb2fcaf1c9..59f5a0f17316 100644
@@ -14,11 +14,11 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
 #ifdef CONFIG_SPARC_LEON
 	if (sparc_cpu_model = sparc_leon)
-		return &dma_direct_ops;
+		return NULL;
 #endif
 #if defined(CONFIG_SPARC32) && defined(CONFIG_PCI)
 	if (bus = &pci_bus_type)
-		return &dma_direct_ops;
+		return NULL;
 #endif
 	return dma_ops;
 }

arch/x86/kernel/pci-dma.c +1 -1

index f4562fcec681..d460998ae828 100644
@@ -17,7 +17,7 @@
 
 static bool disable_dac_quirk __read_mostly;
 
-const struct dma_map_ops *dma_ops = &dma_direct_ops;
+const struct dma_map_ops *dma_ops;
 EXPORT_SYMBOL(dma_ops);
 
 #ifdef CONFIG_IOMMU_DEBUG

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c +1 -1

index 61a84b958d67..50637f372e9f 100644
@@ -581,7 +581,7 @@ static int vmw_dma_select_mode(struct vmw_private *dev_priv)
 
 	dev_priv->map_mode = vmw_dma_map_populate;
 
-	if (dma_ops->sync_single_for_cpu)
+	if (dma_ops && dma_ops->sync_single_for_cpu)
 		dev_priv->map_mode = vmw_dma_alloc_coherent;
 #ifdef CONFIG_SWIOTLB
 	if (swiotlb_nr_tbl() = 0)

drivers/iommu/amd_iommu.c +1 -12

index c5d6c7c42b0a..567221cca13c 100644
@@ -2184,7 +2184,7 @@ static int amd_iommu_add_device(struct device *dev)
 				dev_name(dev));
 
 		iommu_ignore_device(dev);
-		dev->dma_ops = &dma_direct_ops;
+		dev->dma_ops = NULL;
 		goto out;
 	}
 	init_iommu_group(dev);

@@ -2770,17 +2770,6 @@ int __init amd_iommu_init_dma_ops(void)
 	swiotlb        = (iommu_pass_through || sme_me_mask) ? 1 : 0;
 	iommu_detected = 1;
 
-	/*
-	 * In case we don't initialize SWIOTLB (actually the common case
-	 * when AMD IOMMU is enabled and SME is not active), make sure there
-	 * are global dma_ops set as a fall-back for devices not handled by
-	 * this driver (for example non-PCI devices). When SME is active,
-	 * make sure that swiotlb variable remains set so the global dma_ops
-	 * continue to be SWIOTLB.
-	 */
-	if (!swiotlb)
-		dma_ops = &dma_direct_ops;
-
 	if (amd_iommu_unmap_flush)
 		pr_info("AMD-Vi: IO/TLB flush on unmap enabled\n");
 	else

include/asm-generic/dma-mapping.h +1 -1

index 880a292d792f..c13f46109e88 100644
@@ -4,7 +4,7 @@
 
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
-	return &dma_direct_ops;
+	return NULL;
 }
 
 #endif /* _ASM_GENERIC_DMA_MAPPING_H */

include/linux/dma-direct.h +0 -17

index 3b0a3ea3876d..b7338702592a 100644
@@ -60,22 +60,5 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
 struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs);
 void __dma_direct_free_pages(struct device *dev, size_t size, struct page *page);
-dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
-		unsigned long offset, size_t size, enum dma_data_direction dir,
-		unsigned long attrs);
-void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
-		size_t size, enum dma_data_direction dir, unsigned long attrs);
-int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
-		enum dma_data_direction dir, unsigned long attrs);
-void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
-		int nents, enum dma_data_direction dir, unsigned long attrs);
-void dma_direct_sync_single_for_device(struct device *dev,
-		dma_addr_t addr, size_t size, enum dma_data_direction dir);
-void dma_direct_sync_sg_for_device(struct device *dev,
-		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
-void dma_direct_sync_single_for_cpu(struct device *dev,
-		dma_addr_t addr, size_t size, enum dma_data_direction dir);
-void dma_direct_sync_sg_for_cpu(struct device *dev,
-		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
 int dma_direct_supported(struct device *dev, u64 mask);
 #endif /* _LINUX_DMA_DIRECT_H */

include/linux/dma-mapping.h +97 -14

index 269ee27fc3d9..f422aec0f53c 100644
@@ -134,7 +134,6 @@ struct dma_map_ops {
 
 #define DMA_MAPPING_ERROR		(~(dma_addr_t)0)
 
-extern const struct dma_map_ops dma_direct_ops;
 extern const struct dma_map_ops dma_virt_ops;
 extern const struct dma_map_ops dma_dummy_ops;
 

@@ -222,6 +221,69 @@ static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
 }
 #endif
 
+static inline bool dma_is_direct(const struct dma_map_ops *ops)
+{
+	return likely(!ops);
+}
+
+/*
+ * All the dma_direct_* declarations are here just for the indirect call bypass,
+ * and must not be used directly drivers!
+ */
+dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		unsigned long attrs);
+int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
+		enum dma_data_direction dir, unsigned long attrs);
+
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
+    defined(CONFIG_SWIOTLB)
+void dma_direct_sync_single_for_device(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir);
+void dma_direct_sync_sg_for_device(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
+#else
+static inline void dma_direct_sync_single_for_device(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir)
+{
+}
+static inline void dma_direct_sync_sg_for_device(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir)
+{
+}
+#endif
+
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
+    defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) || \
+    defined(CONFIG_SWIOTLB)
+void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs);
+void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
+		int nents, enum dma_data_direction dir, unsigned long attrs);
+void dma_direct_sync_single_for_cpu(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir);
+void dma_direct_sync_sg_for_cpu(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
+#else
+static inline void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+}
+static inline void dma_direct_unmap_sg(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir,
+		unsigned long attrs)
+{
+}
+static inline void dma_direct_sync_single_for_cpu(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir)
+{
+}
+static inline void dma_direct_sync_sg_for_cpu(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir)
+{
+}
+#endif
+
 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 					      size_t size,
 					      enum dma_data_direction dir,

@@ -232,9 +294,12 @@ static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 
 	BUG_ON(!valid_dma_direction(dir));
 	debug_dma_map_single(dev, ptr, size);
-	addr = ops->map_page(dev, virt_to_page(ptr),
-			     offset_in_page(ptr), size,
-			     dir, attrs);
+	if (dma_is_direct(ops))
+		addr = dma_direct_map_page(dev, virt_to_page(ptr),
+				offset_in_page(ptr), size, dir, attrs);
+	else
+		addr = ops->map_page(dev, virt_to_page(ptr),
+				offset_in_page(ptr), size, dir, attrs);
 	debug_dma_map_page(dev, virt_to_page(ptr),
 			   offset_in_page(ptr), size,
 			   dir, addr, true);

@@ -249,7 +314,9 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->unmap_page)
+	if (dma_is_direct(ops))
+		dma_direct_unmap_page(dev, addr, size, dir, attrs);
+	else if (ops->unmap_page)
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	debug_dma_unmap_page(dev, addr, size, dir, true);
 }

@@ -272,7 +339,10 @@ static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 	int ents;
 
 	BUG_ON(!valid_dma_direction(dir));
-	ents = ops->map_sg(dev, sg, nents, dir, attrs);
+	if (dma_is_direct(ops))
+		ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
+	else
+		ents = ops->map_sg(dev, sg, nents, dir, attrs);
 	BUG_ON(ents < 0);
 	debug_dma_map_sg(dev, sg, nents, ents, dir);
 

@@ -287,7 +357,9 @@ static inline void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg
 
 	BUG_ON(!valid_dma_direction(dir));
 	debug_dma_unmap_sg(dev, sg, nents, dir);
-	if (ops->unmap_sg)
+	if (dma_is_direct(ops))
+		dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
+	else if (ops->unmap_sg)
 		ops->unmap_sg(dev, sg, nents, dir, attrs);
 }
 

@@ -301,7 +373,10 @@ static inline dma_addr_t dma_map_page_attrs(struct device *dev,
 	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
-	addr = ops->map_page(dev, page, offset, size, dir, attrs);
+	if (dma_is_direct(ops))
+		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
+	else
+		addr = ops->map_page(dev, page, offset, size, dir, attrs);
 	debug_dma_map_page(dev, page, offset, size, dir, addr, false);
 
 	return addr;

@@ -322,7 +397,7 @@ static inline dma_addr_t dma_map_resource(struct device *dev,
 	BUG_ON(pfn_valid(PHYS_PFN(phys_addr)));
 
 	addr = phys_addr;
-	if (ops->map_resource)
+	if (ops && ops->map_resource)
 		addr = ops->map_resource(dev, phys_addr, size, dir, attrs);
 
 	debug_dma_map_resource(dev, phys_addr, size, dir, addr);

@@ -337,7 +412,7 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->unmap_resource)
+	if (ops && ops->unmap_resource)
 		ops->unmap_resource(dev, addr, size, dir, attrs);
 	debug_dma_unmap_resource(dev, addr, size, dir);
 }

@@ -349,7 +424,9 @@ static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_single_for_cpu)
+	if (dma_is_direct(ops))
+		dma_direct_sync_single_for_cpu(dev, addr, size, dir);
+	else if (ops->sync_single_for_cpu)
 		ops->sync_single_for_cpu(dev, addr, size, dir);
 	debug_dma_sync_single_for_cpu(dev, addr, size, dir);
 }

@@ -368,7 +445,9 @@ static inline void dma_sync_single_for_device(struct device *dev,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_single_for_device)
+	if (dma_is_direct(ops))
+		dma_direct_sync_single_for_device(dev, addr, size, dir);
+	else if (ops->sync_single_for_device)
 		ops->sync_single_for_device(dev, addr, size, dir);
 	debug_dma_sync_single_for_device(dev, addr, size, dir);
 }

@@ -387,7 +466,9 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_sg_for_cpu)
+	if (dma_is_direct(ops))
+		dma_direct_sync_sg_for_cpu(dev, sg, nelems, dir);
+	else if (ops->sync_sg_for_cpu)
 		ops->sync_sg_for_cpu(dev, sg, nelems, dir);
 	debug_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
 }

@@ -399,7 +480,9 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_sg_for_device)
+	if (dma_is_direct(ops))
+		dma_direct_sync_sg_for_device(dev, sg, nelems, dir);
+	else if (ops->sync_sg_for_device)
 		ops->sync_sg_for_device(dev, sg, nelems, dir);
 	debug_dma_sync_sg_for_device(dev, sg, nelems, dir);
 

include/linux/dma-noncoherent.h +4 -1

index 306557331d7d..69b36ed31a99 100644
@@ -38,7 +38,10 @@ pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
 void arch_dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 		enum dma_data_direction direction);
 #else
-#define arch_dma_cache_sync NULL
+static inline void arch_dma_cache_sync(struct device *dev, void *vaddr,
+		size_t size, enum dma_data_direction direction)
+{
+}
 #endif /* CONFIG_DMA_NONCOHERENT_CACHE_SYNC */
 
 #ifdef CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE

kernel/dma/direct.c +8 -29

index 85d8286a0ba2..79da61b49fa4 100644
@@ -223,6 +223,7 @@ void dma_direct_sync_single_for_device(struct device *dev,
 	if (!dev_is_dma_coherent(dev))
 		arch_sync_dma_for_device(dev, paddr, size, dir);
 }
+EXPORT_SYMBOL(dma_direct_sync_single_for_device);
 
 void dma_direct_sync_sg_for_device(struct device *dev,
 		struct scatterlist *sgl, int nents, enum dma_data_direction dir)

@@ -240,6 +241,7 @@ void dma_direct_sync_sg_for_device(struct device *dev,
 					dir);
 	}
 }
+EXPORT_SYMBOL(dma_direct_sync_sg_for_device);
 #endif
 
 #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \

@@ -258,6 +260,7 @@ void dma_direct_sync_single_for_cpu(struct device *dev,
 	if (unlikely(is_swiotlb_buffer(paddr)))
 		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
 }
+EXPORT_SYMBOL(dma_direct_sync_single_for_cpu);
 
 void dma_direct_sync_sg_for_cpu(struct device *dev,
 		struct scatterlist *sgl, int nents, enum dma_data_direction dir)

@@ -277,6 +280,7 @@ void dma_direct_sync_sg_for_cpu(struct device *dev,
 	if (!dev_is_dma_coherent(dev))
 		arch_sync_dma_for_cpu_all(dev);
 }
+EXPORT_SYMBOL(dma_direct_sync_sg_for_cpu);
 
 void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)

@@ -289,6 +293,7 @@ void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
 	if (unlikely(is_swiotlb_buffer(phys)))
 		swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
 }
+EXPORT_SYMBOL(dma_direct_unmap_page);
 
 void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
 		int nents, enum dma_data_direction dir, unsigned long attrs)

@@ -300,11 +305,7 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
 		dma_direct_unmap_page(dev, sg->dma_address, sg_dma_len(sg), dir,
 			     attrs);
 }
-#else
-void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
-		int nents, enum dma_data_direction dir, unsigned long attrs)
-{
-}
+EXPORT_SYMBOL(dma_direct_unmap_sg);
 #endif
 
 static inline bool dma_direct_possible(struct device *dev, dma_addr_t dma_addr,

@@ -331,6 +332,7 @@ dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
 		arch_sync_dma_for_device(dev, phys, size, dir);
 	return dma_addr;
 }
+EXPORT_SYMBOL(dma_direct_map_page);
 
 int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 		enum dma_data_direction dir, unsigned long attrs)

@@ -352,6 +354,7 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 	dma_direct_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
 	return 0;
 }
+EXPORT_SYMBOL(dma_direct_map_sg);
 
 /*
  * Because 32-bit DMA masks are so common we expect every architecture to be

@@ -372,27 +375,3 @@ int dma_direct_supported(struct device *dev, u64 mask)
 
 	return mask >= phys_to_dma(dev, min_mask);
 }
-
-const struct dma_map_ops dma_direct_ops = {
-	.alloc			= dma_direct_alloc,
-	.free			= dma_direct_free,
-	.map_page		= dma_direct_map_page,
-	.map_sg			= dma_direct_map_sg,
-#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
-    defined(CONFIG_SWIOTLB)
-	.sync_single_for_device	= dma_direct_sync_single_for_device,
-	.sync_sg_for_device	= dma_direct_sync_sg_for_device,
-#endif
-#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
-    defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) || \
-    defined(CONFIG_SWIOTLB)
-	.sync_single_for_cpu	= dma_direct_sync_single_for_cpu,
-	.sync_sg_for_cpu	= dma_direct_sync_sg_for_cpu,
-	.unmap_page		= dma_direct_unmap_page,
-	.unmap_sg		= dma_direct_unmap_sg,
-#endif
-	.get_required_mask	= dma_direct_get_required_mask,
-	.dma_supported		= dma_direct_supported,
-	.cache_sync		= arch_dma_cache_sync,
-};
-EXPORT_SYMBOL(dma_direct_ops);

kernel/dma/mapping.c +21 -14

index 0b18cfbdde95..fc84c81029d9 100644
@@ -7,6 +7,7 @@
  */
 #include <linux/memblock.h> /* for max_pfn */
 #include <linux/acpi.h>
+#include <linux/dma-direct.h>
 #include <linux/dma-noncoherent.h>
 #include <linux/export.h>
 #include <linux/gfp.h>

@@ -229,8 +230,8 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
 		unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
-	BUG_ON(!ops);
-	if (ops->get_sgtable)
+
+	if (!dma_is_direct(ops) && ops->get_sgtable)
 		return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
 					attrs);
 	return dma_common_get_sgtable(dev, sgt, cpu_addr, dma_addr, size,

@@ -293,8 +294,8 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 		unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
-	BUG_ON(!ops);
-	if (ops->mmap)
+
+	if (!dma_is_direct(ops) && ops->mmap)
 		return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
 	return dma_common_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
 }

@@ -324,6 +325,8 @@ u64 dma_get_required_mask(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
+	if (dma_is_direct(ops))
+		return dma_direct_get_required_mask(dev);
 	if (ops->get_required_mask)
 		return ops->get_required_mask(dev);
 	return dma_default_get_required_mask(dev);

@@ -341,7 +344,6 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 	void *cpu_addr;
 
-	BUG_ON(!ops);
 	WARN_ON_ONCE(dev && !dev->coherent_dma_mask);
 
 	if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))

@@ -352,10 +354,14 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
 
 	if (!arch_dma_alloc_attrs(&dev))
 		return NULL;
-	if (!ops->alloc)
+
+	if (dma_is_direct(ops))
+		cpu_addr = dma_direct_alloc(dev, size, dma_handle, flag, attrs);
+	else if (ops->alloc)
+		cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
+	else
 		return NULL;
 
-	cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
 	debug_dma_alloc_coherent(dev, size, *dma_handle, cpu_addr);
 	return cpu_addr;
 }

@@ -366,8 +372,6 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	BUG_ON(!ops);
-
 	if (dma_release_from_dev_coherent(dev, get_order(size), cpu_addr))
 		return;
 	/*

@@ -379,11 +383,14 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 	 */
 	WARN_ON(irqs_disabled());
 
-	if (!ops->free || !cpu_addr)
+	if (!cpu_addr)
 		return;
 
 	debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
-	ops->free(dev, size, cpu_addr, dma_handle, attrs);
+	if (dma_is_direct(ops))
+		dma_direct_free(dev, size, cpu_addr, dma_handle, attrs);
+	else if (ops->free)
+		ops->free(dev, size, cpu_addr, dma_handle, attrs);
 }
 EXPORT_SYMBOL(dma_free_attrs);
 

@@ -397,9 +404,9 @@ int dma_supported(struct device *dev, u64 mask)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (!ops)
-		return 0;
-	if (!ops->dma_supported)
+	if (dma_is_direct(ops))
+		return dma_direct_supported(dev, mask);
+	if (ops->dma_supported)
 		return 1;
 	return ops->dma_supported(dev, mask);
 }

@@ -437,7 +444,10 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 	const struct dma_map_ops *ops = get_dma_ops(dev);

Hi Christoph,

Quoted 4 lines · Christoph Hellwig

Avoid expensive indirect calls in the fast path DMA mapping operations by directly calling the dma_direct_* ops if we are using the directly mapped DMA operations.

Quoted 1 line

Signed-off-by Christoph Hellwig <[email protected]>

This breaks direct DMA on ARM64 (also todays linux-next). NULL dev->dma_ops fallbacks to get_arch_dma_ops(), which in turn returns non-functional &dma_dummy_ops on ARM64...

Quoted 11 lines · Marek Szyprowski

Hi Christoph,

Quoted 5 lines · Christoph Hellwig

Avoid expensive indirect calls in the fast path DMA mapping operations by directly calling the dma_direct_* ops if we are using the directly mapped DMA operations.

Signed-off-by Christoph Hellwig <[email protected]>

This breaks direct DMA on ARM64 (also todays linux-next). NULL dev->dma_ops fallbacks to get_arch_dma_ops(), which in turn returns non-functional &dma_dummy_ops on ARM64...

Yeah, fallback from direct (NULL) dev->dma_ops to something else won't work with NULL as the indicator.

Fortunately we shouldn't even need that thanks to the patch from Robin that explicitly set the dummy ops where needed.

Can you try the patch below?

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

index 273e778f7de2..95dbf3ef735a 100644
@@ -26,11 +26,7 @@
 
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)

Avoid expensive indirect calls in the fast path DMA mapping operations by directly calling the dma_direct_* ops if we are using the directly mapped DMA operations.

Hi,

Quoted 4 lines · Christoph Hellwig

Avoid expensive indirect calls in the fast path DMA mapping operations by directly calling the dma_direct_* ops if we are using the directly mapped DMA operations.

This patch results in arm64 boot failures. Reverting the patch fixes the problem. Bisect results are attached. Per logs, the system fails to instantiate the root device. Examples from two logs:

Avoid expensive indirect calls in the fast path DMA mapping operations by directly calling the dma_direct_* ops if we are using the directly mapped DMA operations.

Signed-off-by Christoph Hellwig <[email protected]>

Signed-off-by Christoph Hellwig <[email protected]>

Reported-by Marek Szyprowski <[email protected]>

Tested-by Marek Szyprowski <[email protected]>

---
 arch/alpha/include/asm/dma-mapping.h |   2 +-
 arch/arc/mm/cache.c                  |   2 +-
 arch/arm/include/asm/dma-mapping.h   |   2 +-
 arch/arm/mm/dma-mapping-nommu.c      |  14 +---
 arch/arm64/mm/dma-mapping.c          |   3 -
 arch/ia64/hp/common/hwsw_iommu.c     |   2 +-
 arch/ia64/hp/common/sba_iommu.c      |   4 +-
 arch/ia64/kernel/dma-mapping.c       |   1 -
 arch/mips/include/asm/dma-mapping.h  |   2 +-
 arch/parisc/kernel/setup.c           |   4 -
 arch/sparc/include/asm/dma-mapping.h |   4 +-
 arch/x86/kernel/pci-dma.c            |   2 +-
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c  |   2 +-
 drivers/iommu/amd_iommu.c            |  13 +---
 include/asm-generic/dma-mapping.h    |   2 +-
 include/linux/dma-direct.h           |  17 ----
 include/linux/dma-mapping.h          | 111 +++++++++++++++++++++++----
 include/linux/dma-noncoherent.h      |   5 +-
 kernel/dma/direct.c                  |  37 ++-------
 kernel/dma/mapping.c                 |  40 ++++++----
 20 files changed, 150 insertions(+), 119 deletions(-)

arch/alpha/include/asm/dma-mapping.h +1 -1

index 8beeafd4f68e..0ee6a5c99b16 100644
@@ -7,7 +7,7 @@ extern const struct dma_map_ops alpha_pci_ops;
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
 #ifdef CONFIG_ALPHA_JENSEN
-	return &dma_direct_ops;
+	return NULL;
 #else
 	return &alpha_pci_ops;
 #endif

arch/arc/mm/cache.c +1 -1

index f2701c13a66b..e188bb3ede53 100644
@@ -1280,7 +1280,7 @@ void __init arc_cache_init_master(void)
 	/*
 	 * In case of IOC (say IOC+SLC case), pointers above could still be set
 	 * but end up not being relevant as the first function in chain is not
-	 * called at all for @dma_direct_ops
+	 * called at all for devices using coherent DMA.
 	 *     arch_sync_dma_for_cpu() -> dma_cache_*() -> __dma_cache_*()
 	 */
 }

arch/arm/include/asm/dma-mapping.h +1 -1

index 965b7c846ecb..31d3b96f0f4b 100644
@@ -18,7 +18,7 @@ extern const struct dma_map_ops arm_coherent_dma_ops;
 
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
-	return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : &dma_direct_ops;
+	return IS_ENABLED(CONFIG_MMU) ? &arm_dma_ops : NULL;
 }
 
 #ifdef __arch_page_to_dma

arch/arm/mm/dma-mapping-nommu.c +3 -11

index 712416ecd8e6..f304b10e23a4 100644
@@ -22,7 +22,7 @@
 #include "dma.h"
 
 /*
- *  dma_direct_ops is used if
+ *  The generic direct mapping code is used if
  *   - MMU/MPU is off
  *   - cpu is v7m w/o cache support
  *   - device is coherent

@@ -209,16 +209,9 @@ const struct dma_map_ops arm_nommu_dma_ops = {
 };
 EXPORT_SYMBOL(arm_nommu_dma_ops);
 
-static const struct dma_map_ops *arm_nommu_get_dma_map_ops(bool coherent)
-{
-	return coherent ? &dma_direct_ops : &arm_nommu_dma_ops;
-}
-
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			const struct iommu_ops *iommu, bool coherent)
 {
-	const struct dma_map_ops *dma_ops;
-
 	if (IS_ENABLED(CONFIG_CPU_V7M)) {
 		/*
 		 * Cache support for v7m is optional, so can be treated as

@@ -234,7 +227,6 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 		dev->archdata.dma_coherent = (get_cr() & CR_M) ? coherent : true;
 	}
 
-	dma_ops = arm_nommu_get_dma_map_ops(dev->archdata.dma_coherent);
-
-	set_dma_ops(dev, dma_ops);
+	if (!dev->archdata.dma_coherent)
+		set_dma_ops(dev, &arm_nommu_dma_ops);
 }

arch/arm64/mm/dma-mapping.c +0 -3

index ab1e417204d0..95eda81e3f2d 100644
@@ -462,9 +462,6 @@ static void __iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			const struct iommu_ops *iommu, bool coherent)
 {
-	if (!dev->dma_ops)
-		dev->dma_ops = &dma_direct_ops;
-
 	dev->dma_coherent = coherent;
 	__iommu_setup_dma_ops(dev, dma_base, size, iommu);
 

arch/ia64/hp/common/hwsw_iommu.c +1 -1

index f40ca499b246..8840ed97712f 100644
@@ -38,7 +38,7 @@ static inline int use_swiotlb(struct device *dev)
 const struct dma_map_ops *hwsw_dma_get_ops(struct device *dev)
 {
 	if (use_swiotlb(dev))
-		return &dma_direct_ops;
+		return NULL;
 	return &sba_dma_ops;
 }
 EXPORT_SYMBOL(hwsw_dma_get_ops);

arch/ia64/hp/common/sba_iommu.c +2 -2

index 5ee74820a0f6..5a361e51cb1e 100644
@@ -2078,7 +2078,7 @@ sba_init(void)
 	 * a successful kdump kernel boot is to use the swiotlb.
 	 */
 	if (is_kdump_kernel()) {
-		dma_ops = &dma_direct_ops;
+		dma_ops = NULL;
 		if (swiotlb_late_init_with_default_size(64 * (1<<20)) != 0)
 			panic("Unable to initialize software I/O TLB:"
 				  " Try machvec=dig boot option");

@@ -2100,7 +2100,7 @@ sba_init(void)
 		 * If we didn't find something sba_iommu can claim, we
 		 * need to setup the swiotlb and switch to the dig machvec.
 		 */
-		dma_ops = &dma_direct_ops;
+		dma_ops = NULL;
 		if (swiotlb_late_init_with_default_size(64 * (1<<20)) != 0)
 			panic("Unable to find SBA IOMMU or initialize "
 			      "software I/O TLB: Try machvec=dig boot option");

arch/ia64/kernel/dma-mapping.c +0 -1

index 80cd3e1ea95a..ad7d9963de34 100644
@@ -36,7 +36,6 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
 
 void __init swiotlb_dma_init(void)
 {
-	dma_ops = &dma_direct_ops;
 	swiotlb_init(1);
 }
 #endif

arch/mips/include/asm/dma-mapping.h +1 -1

index 69f914667f3e..20dfaad3a55d 100644
@@ -11,7 +11,7 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 #if defined(CONFIG_MACH_JAZZ)
 	return &jazz_dma_ops;
 #else
-	return &dma_direct_ops;
+	return NULL;
 #endif
 }
 

arch/parisc/kernel/setup.c +0 -4

index cd227f1cf629..54818cd78bd0 100644
@@ -99,10 +99,6 @@ void __init dma_ops_init(void)
 
 	case pcxl2:
 		pa7300lc_init();
-	case pcxl: /* falls through */
-	case pcxs:
-	case pcxt:
-		hppa_dma_ops = &dma_direct_ops;
 		break;
 	default:
 		break;

arch/sparc/include/asm/dma-mapping.h +2 -2

index b0bb2fcaf1c9..59f5a0f17316 100644
@@ -14,11 +14,11 @@ static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
 #ifdef CONFIG_SPARC_LEON
 	if (sparc_cpu_model = sparc_leon)
-		return &dma_direct_ops;
+		return NULL;
 #endif
 #if defined(CONFIG_SPARC32) && defined(CONFIG_PCI)
 	if (bus = &pci_bus_type)
-		return &dma_direct_ops;
+		return NULL;
 #endif
 	return dma_ops;
 }

arch/x86/kernel/pci-dma.c +1 -1

index f4562fcec681..d460998ae828 100644
@@ -17,7 +17,7 @@
 
 static bool disable_dac_quirk __read_mostly;
 
-const struct dma_map_ops *dma_ops = &dma_direct_ops;
+const struct dma_map_ops *dma_ops;
 EXPORT_SYMBOL(dma_ops);
 
 #ifdef CONFIG_IOMMU_DEBUG

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c +1 -1

index 61a84b958d67..50637f372e9f 100644
@@ -581,7 +581,7 @@ static int vmw_dma_select_mode(struct vmw_private *dev_priv)
 
 	dev_priv->map_mode = vmw_dma_map_populate;
 
-	if (dma_ops->sync_single_for_cpu)
+	if (dma_ops && dma_ops->sync_single_for_cpu)
 		dev_priv->map_mode = vmw_dma_alloc_coherent;
 #ifdef CONFIG_SWIOTLB
 	if (swiotlb_nr_tbl() = 0)

drivers/iommu/amd_iommu.c +1 -12

index c5d6c7c42b0a..567221cca13c 100644
@@ -2184,7 +2184,7 @@ static int amd_iommu_add_device(struct device *dev)
 				dev_name(dev));
 
 		iommu_ignore_device(dev);
-		dev->dma_ops = &dma_direct_ops;
+		dev->dma_ops = NULL;
 		goto out;
 	}
 	init_iommu_group(dev);

@@ -2770,17 +2770,6 @@ int __init amd_iommu_init_dma_ops(void)
 	swiotlb        = (iommu_pass_through || sme_me_mask) ? 1 : 0;
 	iommu_detected = 1;
 
-	/*
-	 * In case we don't initialize SWIOTLB (actually the common case
-	 * when AMD IOMMU is enabled and SME is not active), make sure there
-	 * are global dma_ops set as a fall-back for devices not handled by
-	 * this driver (for example non-PCI devices). When SME is active,
-	 * make sure that swiotlb variable remains set so the global dma_ops
-	 * continue to be SWIOTLB.
-	 */
-	if (!swiotlb)
-		dma_ops = &dma_direct_ops;
-
 	if (amd_iommu_unmap_flush)
 		pr_info("AMD-Vi: IO/TLB flush on unmap enabled\n");
 	else

include/asm-generic/dma-mapping.h +1 -1

index 880a292d792f..c13f46109e88 100644
@@ -4,7 +4,7 @@
 
 static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
 {
-	return &dma_direct_ops;
+	return NULL;
 }
 
 #endif /* _ASM_GENERIC_DMA_MAPPING_H */

include/linux/dma-direct.h +0 -17

index 3b0a3ea3876d..b7338702592a 100644
@@ -60,22 +60,5 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
 struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs);
 void __dma_direct_free_pages(struct device *dev, size_t size, struct page *page);
-dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
-		unsigned long offset, size_t size, enum dma_data_direction dir,
-		unsigned long attrs);
-void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
-		size_t size, enum dma_data_direction dir, unsigned long attrs);
-int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
-		enum dma_data_direction dir, unsigned long attrs);
-void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
-		int nents, enum dma_data_direction dir, unsigned long attrs);
-void dma_direct_sync_single_for_device(struct device *dev,
-		dma_addr_t addr, size_t size, enum dma_data_direction dir);
-void dma_direct_sync_sg_for_device(struct device *dev,
-		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
-void dma_direct_sync_single_for_cpu(struct device *dev,
-		dma_addr_t addr, size_t size, enum dma_data_direction dir);
-void dma_direct_sync_sg_for_cpu(struct device *dev,
-		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
 int dma_direct_supported(struct device *dev, u64 mask);
 #endif /* _LINUX_DMA_DIRECT_H */

include/linux/dma-mapping.h +97 -14

index 269ee27fc3d9..f422aec0f53c 100644
@@ -134,7 +134,6 @@ struct dma_map_ops {
 
 #define DMA_MAPPING_ERROR		(~(dma_addr_t)0)
 
-extern const struct dma_map_ops dma_direct_ops;
 extern const struct dma_map_ops dma_virt_ops;
 extern const struct dma_map_ops dma_dummy_ops;
 

@@ -222,6 +221,69 @@ static inline const struct dma_map_ops *get_dma_ops(struct device *dev)
 }
 #endif
 
+static inline bool dma_is_direct(const struct dma_map_ops *ops)
+{
+	return likely(!ops);
+}
+
+/*
+ * All the dma_direct_* declarations are here just for the indirect call bypass,
+ * and must not be used directly drivers!
+ */
+dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
+		unsigned long offset, size_t size, enum dma_data_direction dir,
+		unsigned long attrs);
+int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
+		enum dma_data_direction dir, unsigned long attrs);
+
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
+    defined(CONFIG_SWIOTLB)
+void dma_direct_sync_single_for_device(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir);
+void dma_direct_sync_sg_for_device(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
+#else
+static inline void dma_direct_sync_single_for_device(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir)
+{
+}
+static inline void dma_direct_sync_sg_for_device(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir)
+{
+}
+#endif
+
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
+    defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) || \
+    defined(CONFIG_SWIOTLB)
+void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs);
+void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
+		int nents, enum dma_data_direction dir, unsigned long attrs);
+void dma_direct_sync_single_for_cpu(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir);
+void dma_direct_sync_sg_for_cpu(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir);
+#else
+static inline void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+}
+static inline void dma_direct_unmap_sg(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir,
+		unsigned long attrs)
+{
+}
+static inline void dma_direct_sync_single_for_cpu(struct device *dev,
+		dma_addr_t addr, size_t size, enum dma_data_direction dir)
+{
+}
+static inline void dma_direct_sync_sg_for_cpu(struct device *dev,
+		struct scatterlist *sgl, int nents, enum dma_data_direction dir)
+{
+}
+#endif
+
 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 					      size_t size,
 					      enum dma_data_direction dir,

@@ -232,9 +294,12 @@ static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 
 	BUG_ON(!valid_dma_direction(dir));
 	debug_dma_map_single(dev, ptr, size);
-	addr = ops->map_page(dev, virt_to_page(ptr),
-			     offset_in_page(ptr), size,
-			     dir, attrs);
+	if (dma_is_direct(ops))
+		addr = dma_direct_map_page(dev, virt_to_page(ptr),
+				offset_in_page(ptr), size, dir, attrs);
+	else
+		addr = ops->map_page(dev, virt_to_page(ptr),
+				offset_in_page(ptr), size, dir, attrs);
 	debug_dma_map_page(dev, virt_to_page(ptr),
 			   offset_in_page(ptr), size,
 			   dir, addr, true);

@@ -249,7 +314,9 @@ static inline void dma_unmap_single_attrs(struct device *dev, dma_addr_t addr,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->unmap_page)
+	if (dma_is_direct(ops))
+		dma_direct_unmap_page(dev, addr, size, dir, attrs);
+	else if (ops->unmap_page)
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	debug_dma_unmap_page(dev, addr, size, dir, true);
 }

@@ -272,7 +339,10 @@ static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 	int ents;
 
 	BUG_ON(!valid_dma_direction(dir));
-	ents = ops->map_sg(dev, sg, nents, dir, attrs);
+	if (dma_is_direct(ops))
+		ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
+	else
+		ents = ops->map_sg(dev, sg, nents, dir, attrs);
 	BUG_ON(ents < 0);
 	debug_dma_map_sg(dev, sg, nents, ents, dir);
 

@@ -287,7 +357,9 @@ static inline void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg
 
 	BUG_ON(!valid_dma_direction(dir));
 	debug_dma_unmap_sg(dev, sg, nents, dir);
-	if (ops->unmap_sg)
+	if (dma_is_direct(ops))
+		dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
+	else if (ops->unmap_sg)
 		ops->unmap_sg(dev, sg, nents, dir, attrs);
 }
 

@@ -301,7 +373,10 @@ static inline dma_addr_t dma_map_page_attrs(struct device *dev,
 	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
-	addr = ops->map_page(dev, page, offset, size, dir, attrs);
+	if (dma_is_direct(ops))
+		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
+	else
+		addr = ops->map_page(dev, page, offset, size, dir, attrs);
 	debug_dma_map_page(dev, page, offset, size, dir, addr, false);
 
 	return addr;

@@ -322,7 +397,7 @@ static inline dma_addr_t dma_map_resource(struct device *dev,
 	BUG_ON(pfn_valid(PHYS_PFN(phys_addr)));
 
 	addr = phys_addr;
-	if (ops->map_resource)
+	if (ops && ops->map_resource)
 		addr = ops->map_resource(dev, phys_addr, size, dir, attrs);
 
 	debug_dma_map_resource(dev, phys_addr, size, dir, addr);

@@ -337,7 +412,7 @@ static inline void dma_unmap_resource(struct device *dev, dma_addr_t addr,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->unmap_resource)
+	if (ops && ops->unmap_resource)
 		ops->unmap_resource(dev, addr, size, dir, attrs);
 	debug_dma_unmap_resource(dev, addr, size, dir);
 }

@@ -349,7 +424,9 @@ static inline void dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_single_for_cpu)
+	if (dma_is_direct(ops))
+		dma_direct_sync_single_for_cpu(dev, addr, size, dir);
+	else if (ops->sync_single_for_cpu)
 		ops->sync_single_for_cpu(dev, addr, size, dir);
 	debug_dma_sync_single_for_cpu(dev, addr, size, dir);
 }

@@ -368,7 +445,9 @@ static inline void dma_sync_single_for_device(struct device *dev,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_single_for_device)
+	if (dma_is_direct(ops))
+		dma_direct_sync_single_for_device(dev, addr, size, dir);
+	else if (ops->sync_single_for_device)
 		ops->sync_single_for_device(dev, addr, size, dir);
 	debug_dma_sync_single_for_device(dev, addr, size, dir);
 }

@@ -387,7 +466,9 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_sg_for_cpu)
+	if (dma_is_direct(ops))
+		dma_direct_sync_sg_for_cpu(dev, sg, nelems, dir);
+	else if (ops->sync_sg_for_cpu)
 		ops->sync_sg_for_cpu(dev, sg, nelems, dir);
 	debug_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
 }

@@ -399,7 +480,9 @@ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->sync_sg_for_device)
+	if (dma_is_direct(ops))
+		dma_direct_sync_sg_for_device(dev, sg, nelems, dir);
+	else if (ops->sync_sg_for_device)
 		ops->sync_sg_for_device(dev, sg, nelems, dir);
 	debug_dma_sync_sg_for_device(dev, sg, nelems, dir);
 

include/linux/dma-noncoherent.h +4 -1

index 306557331d7d..69b36ed31a99 100644
@@ -38,7 +38,10 @@ pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
 void arch_dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 		enum dma_data_direction direction);
 #else
-#define arch_dma_cache_sync NULL
+static inline void arch_dma_cache_sync(struct device *dev, void *vaddr,
+		size_t size, enum dma_data_direction direction)
+{
+}
 #endif /* CONFIG_DMA_NONCOHERENT_CACHE_SYNC */
 
 #ifdef CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE

kernel/dma/direct.c +8 -29

index 85d8286a0ba2..79da61b49fa4 100644
@@ -223,6 +223,7 @@ void dma_direct_sync_single_for_device(struct device *dev,
 	if (!dev_is_dma_coherent(dev))
 		arch_sync_dma_for_device(dev, paddr, size, dir);
 }
+EXPORT_SYMBOL(dma_direct_sync_single_for_device);
 
 void dma_direct_sync_sg_for_device(struct device *dev,
 		struct scatterlist *sgl, int nents, enum dma_data_direction dir)

@@ -240,6 +241,7 @@ void dma_direct_sync_sg_for_device(struct device *dev,
 					dir);
 	}
 }
+EXPORT_SYMBOL(dma_direct_sync_sg_for_device);
 #endif
 
 #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \

@@ -258,6 +260,7 @@ void dma_direct_sync_single_for_cpu(struct device *dev,
 	if (unlikely(is_swiotlb_buffer(paddr)))
 		swiotlb_tbl_sync_single(dev, paddr, size, dir, SYNC_FOR_CPU);
 }
+EXPORT_SYMBOL(dma_direct_sync_single_for_cpu);
 
 void dma_direct_sync_sg_for_cpu(struct device *dev,
 		struct scatterlist *sgl, int nents, enum dma_data_direction dir)

@@ -277,6 +280,7 @@ void dma_direct_sync_sg_for_cpu(struct device *dev,
 	if (!dev_is_dma_coherent(dev))
 		arch_sync_dma_for_cpu_all(dev);
 }
+EXPORT_SYMBOL(dma_direct_sync_sg_for_cpu);
 
 void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)

@@ -289,6 +293,7 @@ void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
 	if (unlikely(is_swiotlb_buffer(phys)))
 		swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
 }
+EXPORT_SYMBOL(dma_direct_unmap_page);
 
 void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
 		int nents, enum dma_data_direction dir, unsigned long attrs)

@@ -300,11 +305,7 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
 		dma_direct_unmap_page(dev, sg->dma_address, sg_dma_len(sg), dir,
 			     attrs);
 }
-#else
-void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
-		int nents, enum dma_data_direction dir, unsigned long attrs)
-{
-}
+EXPORT_SYMBOL(dma_direct_unmap_sg);
 #endif
 
 static inline bool dma_direct_possible(struct device *dev, dma_addr_t dma_addr,

@@ -331,6 +332,7 @@ dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
 		arch_sync_dma_for_device(dev, phys, size, dir);
 	return dma_addr;
 }
+EXPORT_SYMBOL(dma_direct_map_page);
 
 int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 		enum dma_data_direction dir, unsigned long attrs)

@@ -352,6 +354,7 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 	dma_direct_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
 	return 0;
 }
+EXPORT_SYMBOL(dma_direct_map_sg);
 
 /*
  * Because 32-bit DMA masks are so common we expect every architecture to be

@@ -372,27 +375,3 @@ int dma_direct_supported(struct device *dev, u64 mask)
 
 	return mask >= phys_to_dma(dev, min_mask);
 }
-
-const struct dma_map_ops dma_direct_ops = {
-	.alloc			= dma_direct_alloc,
-	.free			= dma_direct_free,
-	.map_page		= dma_direct_map_page,
-	.map_sg			= dma_direct_map_sg,
-#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
-    defined(CONFIG_SWIOTLB)
-	.sync_single_for_device	= dma_direct_sync_single_for_device,
-	.sync_sg_for_device	= dma_direct_sync_sg_for_device,
-#endif
-#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
-    defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) || \
-    defined(CONFIG_SWIOTLB)
-	.sync_single_for_cpu	= dma_direct_sync_single_for_cpu,
-	.sync_sg_for_cpu	= dma_direct_sync_sg_for_cpu,
-	.unmap_page		= dma_direct_unmap_page,
-	.unmap_sg		= dma_direct_unmap_sg,
-#endif
-	.get_required_mask	= dma_direct_get_required_mask,
-	.dma_supported		= dma_direct_supported,
-	.cache_sync		= arch_dma_cache_sync,
-};
-EXPORT_SYMBOL(dma_direct_ops);

kernel/dma/mapping.c +25 -15

index 0b18cfbdde95..fc84c81029d9 100644
@@ -7,6 +7,7 @@
  */
 #include <linux/memblock.h> /* for max_pfn */
 #include <linux/acpi.h>
+#include <linux/dma-direct.h>
 #include <linux/dma-noncoherent.h>
 #include <linux/export.h>
 #include <linux/gfp.h>

@@ -229,8 +230,8 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
 		unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
-	BUG_ON(!ops);
-	if (ops->get_sgtable)
+
+	if (!dma_is_direct(ops) && ops->get_sgtable)
 		return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size,
 					attrs);
 	return dma_common_get_sgtable(dev, sgt, cpu_addr, dma_addr, size,

@@ -293,8 +294,8 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 		unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
-	BUG_ON(!ops);
-	if (ops->mmap)
+
+	if (!dma_is_direct(ops) && ops->mmap)
 		return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
 	return dma_common_mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
 }

@@ -324,6 +325,8 @@ u64 dma_get_required_mask(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
+	if (dma_is_direct(ops))
+		return dma_direct_get_required_mask(dev);
 	if (ops->get_required_mask)
 		return ops->get_required_mask(dev);
 	return dma_default_get_required_mask(dev);

@@ -341,7 +344,6 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 	void *cpu_addr;
 
-	BUG_ON(!ops);
 	WARN_ON_ONCE(dev && !dev->coherent_dma_mask);
 
 	if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr))

@@ -352,10 +354,14 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
 
 	if (!arch_dma_alloc_attrs(&dev))
 		return NULL;
-	if (!ops->alloc)
+
+	if (dma_is_direct(ops))
+		cpu_addr = dma_direct_alloc(dev, size, dma_handle, flag, attrs);
+	else if (ops->alloc)
+		cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
+	else
 		return NULL;
 
-	cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
 	debug_dma_alloc_coherent(dev, size, *dma_handle, cpu_addr);
 	return cpu_addr;
 }

@@ -366,8 +372,6 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	BUG_ON(!ops);
-
 	if (dma_release_from_dev_coherent(dev, get_order(size), cpu_addr))
 		return;
 	/*

@@ -379,11 +383,14 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 	 */
 	WARN_ON(irqs_disabled());
 
-	if (!ops->free || !cpu_addr)
+	if (!cpu_addr)
 		return;
 
 	debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
-	ops->free(dev, size, cpu_addr, dma_handle, attrs);
+	if (dma_is_direct(ops))
+		dma_direct_free(dev, size, cpu_addr, dma_handle, attrs);
+	else if (ops->free)
+		ops->free(dev, size, cpu_addr, dma_handle, attrs);
 }
 EXPORT_SYMBOL(dma_free_attrs);
 

@@ -397,9 +404,9 @@ int dma_supported(struct device *dev, u64 mask)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (!ops)
-		return 0;
-	if (!ops->dma_supported)
+	if (dma_is_direct(ops))
+		return dma_direct_supported(dev, mask);
+	if (ops->dma_supported)
 		return 1;
 	return ops->dma_supported(dev, mask);
 }

@@ -437,7 +444,10 @@ void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (ops->cache_sync)
+
+	if (dma_is_direct(ops))
+		arch_dma_cache_sync(dev, vaddr, size, dir);
+	else if (ops->cache_sync)
 		ops->cache_sync(dev, vaddr, size, dir);
 }
 EXPORT_SYMBOL(dma_cache_sync);