Add MEMORY_DEVICE_COHERENT for coherent device memory mapping

Device memory that is cache coherent from device and CPU point of view. This is used on platforms that have an advanced system bus (like CAPI or CXL). Any page of a process can be migrated to such memory. However, no one should be allowed to pin such memory so that it can always be evicted.

Signed-off-by Alex Sierra <[email protected]>

---
 include/linux/memremap.h |  8 ++++++++
 include/linux/mm.h       | 16 ++++++++++++++++
 mm/memcontrol.c          |  6 +++---
 mm/memory-failure.c      |  8 ++++++--
 mm/memremap.c            |  5 ++++-
 mm/migrate.c             | 21 +++++++++++++--------
 6 files changed, 50 insertions(+), 14 deletions(-)

include/linux/memremap.h +8 -0

index c0e9d35889e8..ff4d398edf35 100644
@@ -39,6 +39,13 @@ struct vmem_altmap {
  * A more complete discussion of unaddressable memory may be found in
  * include/linux/hmm.h and Documentation/vm/hmm.rst.
  *
+ * MEMORY_DEVICE_COHERENT:
+ * Device memory that is cache coherent from device and CPU point of view. This
+ * is used on platforms that have an advanced system bus (like CAPI or CXL). A
+ * driver can hotplug the device memory using ZONE_DEVICE and with that memory
+ * type. Any page of a process can be migrated to such memory. However no one
+ * should be allowed to pin such memory so that it can always be evicted.
+ *
  * MEMORY_DEVICE_FS_DAX:
  * Host memory that has similar access semantics as System RAM i.e. DMA
  * coherent and supports page pinning. In support of coordinating page

@@ -59,6 +66,7 @@ struct vmem_altmap {
 enum memory_type {
 	/* 0 is reserved to catch uninitialized type fields */
 	MEMORY_DEVICE_PRIVATE = 1,
+	MEMORY_DEVICE_COHERENT,
 	MEMORY_DEVICE_FS_DAX,
 	MEMORY_DEVICE_GENERIC,
 	MEMORY_DEVICE_PCI_P2PDMA,

include/linux/mm.h +1 -0

index 73a52aba448f..fcf96c0fc918 100644
@@ -1162,6 +1162,7 @@ static inline bool page_is_devmap_managed(struct page *page)
 		return false;
 	switch (page->pgmap->type) {
 	case MEMORY_DEVICE_PRIVATE:
+	case MEMORY_DEVICE_COHERENT:
 	case MEMORY_DEVICE_FS_DAX:
 		return true;
 	default:

@@ -1191,6 +1192,21 @@ static inline bool is_device_private_page(const struct page *page)
 		page->pgmap->type == MEMORY_DEVICE_PRIVATE;

include/linux/mm.h +7 -0

+{
+	return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
+		is_zone_device_page(page) &&
+		(page->pgmap->type == MEMORY_DEVICE_PRIVATE ||
+		page->pgmap->type == MEMORY_DEVICE_COHERENT);
+}
+
 static inline bool is_pci_p2pdma_page(const struct page *page)
 {
 	return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&

mm/memcontrol.c +3 -3

index 6da5020a8656..d0bab0747c73 100644
@@ -5695,8 +5695,8 @@ static int mem_cgroup_move_account(struct page *page,
  *   2(MC_TARGET_SWAP): if the swap entry corresponding to this pte is a
  *     target for charge migration. if @target is not NULL, the entry is stored
  *     in target->ent.
- *   3(MC_TARGET_DEVICE): like MC_TARGET_PAGE  but page is MEMORY_DEVICE_PRIVATE
- *     (so ZONE_DEVICE page and thus not on the lru).
+ *   3(MC_TARGET_DEVICE): like MC_TARGET_PAGE  but page is device memory and
+ *   thus not on the lru.
  *     For now we such page is charge like a regular page would be as for all
  *     intent and purposes it is just special memory taking the place of a
  *     regular page.

@@ -5730,7 +5730,7 @@ static enum mc_target_type get_mctgt_type(struct vm_area_struct *vma,
 		 */
 		if (page_memcg(page) == mc.from) {
 			ret = MC_TARGET_PAGE;
-			if (is_device_private_page(page))
+			if (is_device_page(page))
 				ret = MC_TARGET_DEVICE;
 			if (target)
 				target->page = page;

mm/memory-failure.c +6 -2

index 3e6449f2102a..4cf212e5f432 100644
@@ -1554,12 +1554,16 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
 		goto unlock;
 	}
 
-	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
+	switch (pgmap->type) {
+	case MEMORY_DEVICE_PRIVATE:
+	case MEMORY_DEVICE_COHERENT:
 		/*
-		 * TODO: Handle HMM pages which may need coordination
+		 * TODO: Handle device pages which may need coordination
 		 * with device-side memory.
 		 */
 		goto unlock;
+	default:
+		break;
 	}
 
 	/*

mm/memremap.c +2 -0

index ed593bf87109..94d6a1e01d42 100644
@@ -44,6 +44,7 @@ EXPORT_SYMBOL(devmap_managed_key);
 static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
 {
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+	    pgmap->type == MEMORY_DEVICE_COHERENT ||
 	    pgmap->type == MEMORY_DEVICE_FS_DAX)
 		static_branch_dec(&devmap_managed_key);
 }

@@ -51,6 +52,7 @@ static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
 static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
 {
 	if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+	    pgmap->type == MEMORY_DEVICE_COHERENT ||
 	    pgmap->type == MEMORY_DEVICE_FS_DAX)
 		static_branch_inc(&devmap_managed_key);
 }

mm/memremap.c +1 -1

@@ -498,7 +501,7 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap);
 void free_devmap_managed_page(struct page *page)
 {
 	/* notify page idle for dax */
-	if (!is_device_private_page(page)) {
+	if (!is_device_page(page)) {
 		wake_up_var(&page->_refcount);
 		return;
 	}

mm/migrate.c +3 -3

index 1852d787e6ab..91018880dc7f 100644
@@ -362,7 +362,7 @@ static int expected_page_refs(struct address_space *mapping, struct page *page)
 	 * Device private pages have an extra refcount as they are
 	 * ZONE_DEVICE pages.
 	 */
-	expected_count += is_device_private_page(page);
+	expected_count += is_device_page(page);
 	if (mapping)
 		expected_count += thp_nr_pages(page) + page_has_private(page);
 

@@ -2503,7 +2503,7 @@ static bool migrate_vma_check_page(struct page *page)
 		 * FIXME proper solution is to rework migration_entry_wait() so
 		 * it does not need to take a reference on page.
 		 */
-		return is_device_private_page(page);
+		return is_device_page(page);
 	}
 	/* For file back page */

@@ -2791,7 +2791,7 @@ EXPORT_SYMBOL(migrate_vma_setup);
  *     handle_pte_fault()
  *       do_anonymous_page()
  * to map in an anonymous zero page but the struct page will be a ZONE_DEVICE
- * private page.
+ * private or coherent page.
  */
 static void migrate_vma_insert_page(struct migrate_vma *migrate,
 				    unsigned long addr,

mm/migrate.c +5 -5

 		} else {
 			/*
-			 * For now we only support migrating to un-addressable
-			 * device memory.
+			 * We support migrating to private and coherent types
+			 * for device zone memory.
 			 */
 			pr_warn_once("Unsupported ZONE_DEVICE page type.\n");
 			goto abort;

@@ -2976,10 +2981,10 @@ void migrate_vma_pages(struct migrate_vma *migrate)
 		mapping = page_mapping(page);
 
 		if (is_zone_device_page(newpage)) {
-			if (is_device_private_page(newpage)) {
+			if (is_device_page(newpage)) {
 				/*
-				 * For now only support private anonymous when
-				 * migrating to un-addressable device memory.
+				 * For now only support private and coherent
+				 * anonymous when migrating to device memory.
 				 */
 				if (mapping) {
 					migrate->src[i] &= ~MIGRATE_PFN_MIGRATE;

Avoid long term pinning for Coherent device type pages. This could interfere with their own device memory manager. For now, we are just returning error for PIN_LONGTERM Coherent device type pages. Eventually, these type of pages will get migrated to system memory, once the device migration pages support is added.

Signed-off-by Alex Sierra <[email protected]>

---
 mm/gup.c | 7 +++++++
 1 file changed, 7 insertions(+)

mm/gup.c +0 -0

index 886d6148d3d0..9c8a075d862d 100644

Quoted 11 lines · Alex Sierra

Avoid long term pinning for Coherent device type pages. This could interfere with their own device memory manager. For now, we are just returning error for PIN_LONGTERM Coherent device type pages. Eventually, these type of pages will get migrated to system memory, once the device migration pages support is added.

Signed-off-by Alex Sierra <[email protected]>

---
 mm/gup.c | 7 +++++++
 1 file changed, 7 insertions(+)

Quoted 5 lines

mm/gup.c +0 -0

index 886d6148d3d0..9c8a075d862d 100644

mm/gup.c static long check_and_migrate_movable_pages(unsigned long nr_pages, · line 1728

Quoted 9 lines

mm/gup.c +6 -0

@@ -1720,6 +1720,12 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
 		 * If we get a movable page, since we are going to be pinning
 		 * these entries, try to move them out if possible.
 		 */
+		if (is_device_page(head)) {
+			WARN_ON_ONCE(is_device_private_page(head));
+			ret = -EFAULT;
+			goto unpin_pages;
+		}
+

Wouldn't be more efficient for you failing earlier instead of after all the pages are pinned?

Filesystem DAX suffers from a somewhat similar issue[0] -- albeit it's more related to blocking FOLL_LONGTERM in gup-fast while gup-slow can still do it. Coherent devmap appears to want to block it in all gup.

On another thread Jason was suggesting about having different pgmap::flags to capture these special cases[1] instead of selecting what different pgmap types can do in various different places.

[0] https://lore.kernel.org/linux-mm/[email protected]/
[1] https://lore.kernel.org/linux-mm/[email protected]/

lib/test_hmm_uapi.h +3 -0

+	HMM_DMIRROR_MEMORY_DEVICE_PRIVATE = 1,
+};
+
 #endif /* _LIB_TEST_HMM_UAPI_H */

In order to configure device coherent in test_hmm, two module parameters should be passed, which correspond to the SP start address of each device (2) spm_addr_dev0 & spm_addr_dev1. If no parameters are passed, private device type is configured.

Signed-off-by Alex Sierra <[email protected]>

---
 lib/test_hmm.c      | 74 +++++++++++++++++++++++++++++++--------------
 lib/test_hmm_uapi.h |  1 +
 2 files changed, 53 insertions(+), 22 deletions(-)

lib/test_hmm.c +0 -0

index 97e48164d56a..9edeff52302e 100644

lib/test_hmm.c +24 -6

+
+static unsigned long spm_addr_dev1;
+module_param(spm_addr_dev1, long, 0644);
+MODULE_PARM_DESC(spm_addr_dev1,
+		"Specify start address for SPM (special purpose memory) used for device 1. By setting this Coherent device type will be used. Make sure spm_addr_dev0 is set too");
+
 static const struct dev_pagemap_ops dmirror_devmem_ops;
 static const struct mmu_interval_notifier_ops dmirror_min_ops;
 static dev_t dmirror_dev;

@@ -452,29 +462,44 @@ static int dmirror_write(struct dmirror *dmirror, struct hmm_dmirror_cmd *cmd)
 	return ret;
 }
 
-static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
+static int dmirror_allocate_chunk(struct dmirror_device *mdevice,
 				   struct page **ppage)
 {
 	struct dmirror_chunk *devmem;
-	struct resource *res;
+	struct resource *res = NULL;
 	unsigned long pfn;
 	unsigned long pfn_first;
 	unsigned long pfn_last;
 	void *ptr;
+	int ret = -ENOMEM;
 
 	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
 	if (!devmem)
-		return false;
+		return ret;
 
-	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
-				      "hmm_dmirror");
-	if (IS_ERR(res))
+	switch (mdevice->zone_device_type) {
+	case HMM_DMIRROR_MEMORY_DEVICE_PRIVATE:
+		res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
+					      "hmm_dmirror");
+		if (IS_ERR_OR_NULL(res))
+			goto err_devmem;
+		devmem->pagemap.range.start = res->start;
+		devmem->pagemap.range.end = res->end;
+		devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+		break;
+	case HMM_DMIRROR_MEMORY_DEVICE_COHERENT:
+		devmem->pagemap.range.start = (MINOR(mdevice->cdevice.dev) - 2) ?
+							spm_addr_dev0 :
+							spm_addr_dev1;

lib/test_hmm.c +17 -15

-	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
-	devmem->pagemap.range.start = res->start;
-	devmem->pagemap.range.end = res->end;
 	devmem->pagemap.nr_range = 1;
 	devmem->pagemap.ops = &dmirror_devmem_ops;
 	devmem->pagemap.owner = mdevice;

@@ -495,10 +520,14 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 		mdevice->devmem_capacity = new_capacity;
 		mdevice->devmem_chunks = new_chunks;
 	}
-
 	ptr = memremap_pages(&devmem->pagemap, numa_node_id());
-	if (IS_ERR(ptr))
+	if (IS_ERR_OR_NULL(ptr)) {
+		if (ptr)
+			ret = PTR_ERR(ptr);
+		else
+			ret = -EFAULT;
 		goto err_release;
+	}
 
 	devmem->mdevice = mdevice;
 	pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;

@@ -527,15 +556,17 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 	}
 	spin_unlock(&mdevice->lock);
 
-	return true;
+	return 0;
 
 err_release:
 	mutex_unlock(&mdevice->devmem_lock);
-	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
+	if (res && devmem->pagemap.type == MEMORY_DEVICE_PRIVATE)
+		release_mem_region(devmem->pagemap.range.start,
+				   range_len(&devmem->pagemap.range));
 err_devmem:
 	kfree(devmem);
 
-	return false;
+	return ret;
 }
 
 static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)

@@ -560,7 +591,7 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)
 		spin_unlock(&mdevice->lock);
 	} else {
 		spin_unlock(&mdevice->lock);
-		if (!dmirror_allocate_chunk(mdevice, &dpage))
+		if (dmirror_allocate_chunk(mdevice, &dpage))
 			goto error;
 	}
 

@@ -1220,10 +1251,8 @@ static int dmirror_device_init(struct dmirror_device *mdevice, int id)
 	if (ret)
 		return ret;
 
-	/* Build a list of free ZONE_DEVICE private struct pages */
-	dmirror_allocate_chunk(mdevice, NULL);
-
-	return 0;
+	/* Build a list of free ZONE_DEVICE struct pages */
+	return dmirror_allocate_chunk(mdevice, NULL);
 }
 
 static void dmirror_device_remove(struct dmirror_device *mdevice)

@@ -1236,8 +1265,9 @@ static void dmirror_device_remove(struct dmirror_device *mdevice)
 				mdevice->devmem_chunks[i];
 
 			memunmap_pages(&devmem->pagemap);
-			release_mem_region(devmem->pagemap.range.start,
-					   range_len(&devmem->pagemap.range));
+			if (devmem->pagemap.type == MEMORY_DEVICE_PRIVATE)
+				release_mem_region(devmem->pagemap.range.start,
+						   range_len(&devmem->pagemap.range));
 			kfree(devmem);
 		}
 		kfree(mdevice->devmem_chunks);

lib/test_hmm_uapi.h +1 -0

index 17f842f1aa02..625f3690d086 100644
@@ -68,6 +68,7 @@ enum {
 enum {
 	/* 0 is reserved to catch uninitialized type fields */
 	HMM_DMIRROR_MEMORY_DEVICE_PRIVATE = 1,
+	HMM_DMIRROR_MEMORY_DEVICE_COHERENT,
 };
 
 #endif /* _LIB_TEST_HMM_UAPI_H */

Device Coherent type uses device memory that is coherently accesible by the CPU. This could be shown as SP (special purpose) memory range at the BIOS-e820 memory enumeration. If no SP memory is supported in system, this could be faked by setting CONFIG_EFI_FAKE_MEMMAP.

Currently, test_hmm only supports two different SP ranges of at least 256MB size. This could be specified in the kernel parameter variable efi_fake_mem. Ex. Two SP ranges of 1GB starting at 0x100000000 & 0x140000000 physical address. Ex. efi_fake_mem=1G@0x100000000:0x40000,1G@0x140000000:0x40000

Private and coherent device mirror instances can be created in the same probed. This is done by passing the module parameters spm_addr_dev0 & spm_addr_dev1. In this case, it will create four instances of device_mirror. The first two correspond to private device type, the last two to coherent type. Then, they can be easily accessed from user space through /dev/hmm_mirror<num_device>. Usually num_device 0 and 1 are for private, and 2 and 3 for coherent types. If no module parameters are passed, two instances of private type device_mirror will be created only.

Signed-off-by Alex Sierra <[email protected]>

---
 lib/test_hmm.c      | 247 ++++++++++++++++++++++++++++++++------------
 lib/test_hmm_uapi.h |  15 ++-
 2 files changed, 193 insertions(+), 69 deletions(-)

lib/test_hmm.c +39 -9

index 9edeff52302e..7c641c5a9cfa 100644
@@ -29,11 +29,22 @@
 
 #include "test_hmm_uapi.h"
 
-#define DMIRROR_NDEVICES		2
+#define DMIRROR_NDEVICES		4
 #define DMIRROR_RANGE_FAULT_TIMEOUT	1000
 #define DEVMEM_CHUNK_SIZE		(256 * 1024 * 1024U)
 #define DEVMEM_CHUNKS_RESERVE		16
 
+/*
+ * For device_private pages, dpage is just a dummy struct page
+ * representing a piece of device memory. dmirror_devmem_alloc_page
+ * allocates a real system memory page as backing storage to fake a
+ * real device. zone_device_data points to that backing page. But
+ * for device_coherent memory, the struct page represents real
+ * physical CPU-accessible memory that we can use directly.
+ */
+#define BACKING_PAGE(page) (is_device_private_page((page)) ? \
+			   (page)->zone_device_data : (page))
+
 static unsigned long spm_addr_dev0;
 module_param(spm_addr_dev0, long, 0644);
 MODULE_PARM_DESC(spm_addr_dev0,

@@ -122,6 +133,21 @@ static int dmirror_bounce_init(struct dmirror_bounce *bounce,
 	return 0;
 }
 
+static bool dmirror_is_private_zone(struct dmirror_device *mdevice)
+{
+	return (mdevice->zone_device_type ==
+		HMM_DMIRROR_MEMORY_DEVICE_PRIVATE) ? true : false;
+}
+
+static enum migrate_vma_direction
+	dmirror_select_device(struct dmirror *dmirror)
+{
+	return (dmirror->mdevice->zone_device_type ==
+		HMM_DMIRROR_MEMORY_DEVICE_PRIVATE) ?
+		MIGRATE_VMA_SELECT_DEVICE_PRIVATE :
+		MIGRATE_VMA_SELECT_DEVICE_COHERENT;
+}
+
 static void dmirror_bounce_fini(struct dmirror_bounce *bounce)
 {
 	vfree(bounce->ptr);

@@ -572,16 +598,19 @@ static int dmirror_allocate_chunk(struct dmirror_device *mdevice,
 static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)
 {
 	struct page *dpage = NULL;
-	struct page *rpage;
+	struct page *rpage = NULL;
 
 	/*
-	 * This is a fake device so we alloc real system memory to store
-	 * our device memory.
+	 * For ZONE_DEVICE private type, this is a fake device so we alloc real
+	 * system memory to store our device memory.
+	 * For ZONE_DEVICE coherent type we use the actual dpage to store the data
+	 * and ignore rpage.
 	 */
-	rpage = alloc_page(GFP_HIGHUSER);
-	if (!rpage)
-		return NULL;
-
+	if (dmirror_is_private_zone(mdevice)) {
+		rpage = alloc_page(GFP_HIGHUSER);
+		if (!rpage)
+			return NULL;
+	}
 	spin_lock(&mdevice->lock);
 
 	if (mdevice->free_pages) {

@@ -601,7 +630,8 @@ static struct page *dmirror_devmem_alloc_page(struct dmirror_device *mdevice)
 	return dpage;
 
 error:
-	__free_page(rpage);
+	if (rpage)
+		__free_page(rpage);
 	return NULL;
 }
 

lib/test_hmm.c +12 -8

 		dpage = dmirror_devmem_alloc_page(mdevice);
 		if (!dpage)
 			continue;
 
-		rpage = dpage->zone_device_data;
+		rpage = BACKING_PAGE(dpage);
 		if (spage)
 			copy_highpage(rpage, spage);
 		else

@@ -646,6 +679,8 @@ static void dmirror_migrate_alloc_and_copy(struct migrate_vma *args,
 		 */
 		rpage->zone_device_data = dmirror;
 
+		pr_debug("migrating from sys to dev pfn src: 0x%lx pfn dst: 0x%lx\n",
+			 page_to_pfn(spage), page_to_pfn(dpage));
 		*dst = migrate_pfn(page_to_pfn(dpage)) |
 			    MIGRATE_PFN_LOCKED;
 		if ((*src & MIGRATE_PFN_WRITE) ||

@@ -724,11 +759,7 @@ static int dmirror_migrate_finalize_and_map(struct migrate_vma *args,
 		if (!dpage)
 			continue;
 
-		/*
-		 * Store the page that holds the data so the page table
-		 * doesn't have to deal with ZONE_DEVICE private pages.
-		 */
-		entry = dpage->zone_device_data;
+		entry = BACKING_PAGE(dpage);
 		if (*dst & MIGRATE_PFN_WRITE)
 			entry = xa_tag_pointer(entry, DPT_XA_TAG_WRITE);
 		entry = xa_store(&dmirror->pt, pfn, entry, GFP_ATOMIC);

@@ -808,8 +839,101 @@ static int dmirror_exclusive(struct dmirror *dmirror,
 	return ret;
 }
 
-static int dmirror_migrate(struct dmirror *dmirror,
-			   struct hmm_dmirror_cmd *cmd)
+static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
+						      struct dmirror *dmirror)
+{
+	const unsigned long *src = args->src;
+	unsigned long *dst = args->dst;
+	unsigned long start = args->start;
+	unsigned long end = args->end;
+	unsigned long addr;

lib/test_hmm.c +62 -0

+		spage = BACKING_PAGE(spage);
+		dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);
+		if (!dpage)
+			continue;
+		pr_debug("migrating from dev to sys pfn src: 0x%lx pfn dst: 0x%lx\n",
+			 page_to_pfn(spage), page_to_pfn(dpage));
+
+		lock_page(dpage);
+		xa_erase(&dmirror->pt, addr >> PAGE_SHIFT);
+		copy_highpage(dpage, spage);
+		*dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED;
+		if (*src & MIGRATE_PFN_WRITE)
+			*dst |= MIGRATE_PFN_WRITE;
+	}
+	return 0;
+}
+
+static int dmirror_migrate_to_system(struct dmirror *dmirror,
+				     struct hmm_dmirror_cmd *cmd)
+{
+	unsigned long start, end, addr;
+	unsigned long size = cmd->npages << PAGE_SHIFT;
+	struct mm_struct *mm = dmirror->notifier.mm;
+	struct vm_area_struct *vma;
+	unsigned long src_pfns[64];
+	unsigned long dst_pfns[64];
+	struct migrate_vma args;
+	unsigned long next;
+	int ret;
+
+	start = cmd->addr;
+	end = start + size;
+	if (end < start)
+		return -EINVAL;
+
+	/* Since the mm is for the mirrored process, get a reference first. */
+	if (!mmget_not_zero(mm))
+		return -EINVAL;
+
+	mmap_read_lock(mm);
+	for (addr = start; addr < end; addr = next) {
+		vma = vma_lookup(mm, addr);
+		if (!vma || !(vma->vm_flags & VM_READ)) {
+			ret = -EINVAL;
+			goto out;
+		}
+		next = min(end, addr + (ARRAY_SIZE(src_pfns) << PAGE_SHIFT));
+		if (next > vma->vm_end)
+			next = vma->vm_end;
+
+		args.vma = vma;
+		args.src = src_pfns;
+		args.dst = dst_pfns;
+		args.start = addr;
+		args.end = next;
+		args.pgmap_owner = dmirror->mdevice;
+		args.flags = dmirror_select_device(dmirror);
+
+		ret = migrate_vma_setup(&args);
+		if (ret)
+			goto out;
+

lib/test_hmm.c +6 -1

+}
+
+static int dmirror_migrate_to_device(struct dmirror *dmirror,
+				struct hmm_dmirror_cmd *cmd)
 {
 	unsigned long start, end, addr;
 	unsigned long size = cmd->npages << PAGE_SHIFT;

@@ -853,6 +977,7 @@ static int dmirror_migrate(struct dmirror *dmirror,
 		if (ret)
 			goto out;
 
+		pr_debug("Migrating from sys mem to device mem\n");
 		dmirror_migrate_alloc_and_copy(&args, dmirror);
 		migrate_vma_pages(&args);
 		dmirror_migrate_finalize_and_map(&args, dmirror);

@@ -861,7 +986,7 @@ static int dmirror_migrate(struct dmirror *dmirror,
 	mmap_read_unlock(mm);
 	mmput(mm);
 
-	/* Return the migrated data for verification. */
+	/* Return the migrated data for verification. only for pages in device zone */
 	ret = dmirror_bounce_init(&bounce, start, size);
 	if (ret)
 		return ret;

lib/test_hmm.c +19 -38

+			if (dmirror->mdevice == dmirror_page_to_device(page))
+				*perm = HMM_DMIRROR_PROT_DEV_COHERENT_LOCAL;
+			else
+				*perm = HMM_DMIRROR_PROT_DEV_COHERENT_REMOTE;
+		/*
+		 * Is page ZONE_DEVICE private migrated to
+		 * this device or some other?
+		 */
+		} else if (dmirror->mdevice == dmirror_page_to_device(page)) {
 			*perm = HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL;
-		else
+		} else {
 			*perm = HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE;
+		}
 	} else if (is_zero_pfn(page_to_pfn(page)))
 		*perm = HMM_DMIRROR_PROT_ZERO;
 	else

@@ -1100,8 +1235,12 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp,
 		ret = dmirror_write(dmirror, &cmd);
 		break;
 
-	case HMM_DMIRROR_MIGRATE:
-		ret = dmirror_migrate(dmirror, &cmd);
+	case HMM_DMIRROR_MIGRATE_TO_DEV:
+		ret = dmirror_migrate_to_device(dmirror, &cmd);
+		break;
+
+	case HMM_DMIRROR_MIGRATE_TO_SYS:
+		ret = dmirror_migrate_to_system(dmirror, &cmd);
 		break;
 
 	case HMM_DMIRROR_EXCLUSIVE:

@@ -1142,14 +1281,13 @@ static const struct file_operations dmirror_fops = {
 
 static void dmirror_devmem_free(struct page *page)
 {
-	struct page *rpage = page->zone_device_data;
+	struct page *rpage = BACKING_PAGE(page);
 	struct dmirror_device *mdevice;
 
-	if (rpage)
+	if (rpage != page)
 		__free_page(rpage);
 
 	mdevice = dmirror_page_to_device(page);
-
 	spin_lock(&mdevice->lock);
 	mdevice->cfree++;
 	page->zone_device_data = mdevice->free_pages;

@@ -1157,38 +1295,6 @@ static void dmirror_devmem_free(struct page *page)
 	spin_unlock(&mdevice->lock);
 }
 
-static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
-						      struct dmirror *dmirror)
-{
-	const unsigned long *src = args->src;
-	unsigned long *dst = args->dst;
-	unsigned long start = args->start;
-	unsigned long end = args->end;
-	unsigned long addr;
-
-	for (addr = start; addr < end; addr += PAGE_SIZE,
-				       src++, dst++) {
-		struct page *dpage, *spage;
-
-		spage = migrate_pfn_to_page(*src);
-		if (!spage || !(*src & MIGRATE_PFN_MIGRATE))
-			continue;
-		spage = spage->zone_device_data;
-
-		dpage = alloc_page_vma(GFP_HIGHUSER_MOVABLE, args->vma, addr);
-		if (!dpage)
-			continue;
-
-		lock_page(dpage);
-		xa_erase(&dmirror->pt, addr >> PAGE_SHIFT);
-		copy_highpage(dpage, spage);
-		*dst = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED;
-		if (*src & MIGRATE_PFN_WRITE)
-			*dst |= MIGRATE_PFN_WRITE;
-	}
-	return 0;
-}
-
 static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
 {
 	struct migrate_vma args;

lib/test_hmm.c +15 -3

 	dmirror = rpage->zone_device_data;
 
 	/* FIXME demonstrate how we can adjust migrate range */

@@ -1213,7 +1319,7 @@ static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
 	args.src = &src_pfns;
 	args.dst = &dst_pfns;
 	args.pgmap_owner = dmirror->mdevice;
-	args.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;
+	args.flags = dmirror_select_device(dmirror);
 
 	if (migrate_vma_setup(&args))
 		return VM_FAULT_SIGBUS;

@@ -1279,14 +1385,26 @@ static void dmirror_device_remove(struct dmirror_device *mdevice)
 static int __init hmm_dmirror_init(void)
 {
 	int ret;
-	int id;
+	int id = 0;
+	int ndevices = 0;
 
 	ret = alloc_chrdev_region(&dmirror_dev, 0, DMIRROR_NDEVICES,
 				  "HMM_DMIRROR");
 	if (ret)
 		goto err_unreg;
 
-	for (id = 0; id < DMIRROR_NDEVICES; id++) {
+	memset(dmirror_devices, 0, DMIRROR_NDEVICES * sizeof(dmirror_devices[0]));
+	dmirror_devices[ndevices++].zone_device_type =
+				HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
+	dmirror_devices[ndevices++].zone_device_type =
+				HMM_DMIRROR_MEMORY_DEVICE_PRIVATE;
+	if (spm_addr_dev0 && spm_addr_dev1) {
+		dmirror_devices[ndevices++].zone_device_type =
+					HMM_DMIRROR_MEMORY_DEVICE_COHERENT;
+		dmirror_devices[ndevices++].zone_device_type =
+					HMM_DMIRROR_MEMORY_DEVICE_COHERENT;
+	}
+	for (id = 0; id < ndevices; id++) {
 		ret = dmirror_device_init(dmirror_devices + id, id);
 		if (ret)
 			goto err_chrdev;

lib/test_hmm.c +1 -0

+			dmirror_device_remove(dmirror_devices + id);
 	unregister_chrdev_region(dmirror_dev, DMIRROR_NDEVICES);
 }
 

lib/test_hmm_uapi.h +10 -5

index 625f3690d086..e190b2ab6f19 100644
@@ -33,11 +33,12 @@ struct hmm_dmirror_cmd {
 /* Expose the address space of the calling process through hmm device file */
 #define HMM_DMIRROR_READ		_IOWR('H', 0x00, struct hmm_dmirror_cmd)
 #define HMM_DMIRROR_WRITE		_IOWR('H', 0x01, struct hmm_dmirror_cmd)
-#define HMM_DMIRROR_MIGRATE		_IOWR('H', 0x02, struct hmm_dmirror_cmd)
-#define HMM_DMIRROR_SNAPSHOT		_IOWR('H', 0x03, struct hmm_dmirror_cmd)
-#define HMM_DMIRROR_EXCLUSIVE		_IOWR('H', 0x04, struct hmm_dmirror_cmd)
-#define HMM_DMIRROR_CHECK_EXCLUSIVE	_IOWR('H', 0x05, struct hmm_dmirror_cmd)
-#define HMM_DMIRROR_GET_MEM_DEV_TYPE	_IOWR('H', 0x06, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_MIGRATE_TO_DEV	_IOWR('H', 0x02, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_MIGRATE_TO_SYS	_IOWR('H', 0x03, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_SNAPSHOT		_IOWR('H', 0x04, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_EXCLUSIVE		_IOWR('H', 0x05, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_CHECK_EXCLUSIVE	_IOWR('H', 0x06, struct hmm_dmirror_cmd)
+#define HMM_DMIRROR_GET_MEM_DEV_TYPE	_IOWR('H', 0x07, struct hmm_dmirror_cmd)
 
 /*
  * Values returned in hmm_dmirror_cmd.ptr for HMM_DMIRROR_SNAPSHOT.

@@ -52,6 +53,8 @@ struct hmm_dmirror_cmd {
  *					device the ioctl() is made
  * HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE: Migrated device private page on some
  *					other device
+ * HMM_DMIRROR_PROT_DEV_COHERENT: Migrate device coherent page on the device
+ *				  the ioctl() is made
  */
 enum {
 	HMM_DMIRROR_PROT_ERROR			= 0xFF,

@@ -63,6 +66,8 @@ enum {
 	HMM_DMIRROR_PROT_ZERO			= 0x10,
 	HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL	= 0x20,
 	HMM_DMIRROR_PROT_DEV_PRIVATE_REMOTE	= 0x30,
+	HMM_DMIRROR_PROT_DEV_COHERENT_LOCAL	= 0x40,
+	HMM_DMIRROR_PROT_DEV_COHERENT_REMOTE	= 0x50,
 };
 
 enum {

Test cases such as migrate_fault and migrate_multiple, were modified to explicit migrate from device to sys memory without the need of page faults, when using device coherent type.

Snapshot test case updated to read memory device type first and based on that, get the proper returned results migrate_ping_pong test case

added to test explicit migration from device to sys memory for both private and coherent zone types.

Helpers to migrate from device to sys memory and vicerversa were also added.

Signed-off-by Alex Sierra <[email protected]>

---
v2:
Set FIXTURE_VARIANT to add multiple device types to the FIXTURE. This will run all the tests for each device type (private and coherent) in case both existed during hmm-test driver probed.

---
 tools/testing/selftests/vm/hmm-tests.c | 122 ++++++++++++++++++++-----
 1 file changed, 101 insertions(+), 21 deletions(-)

tools/testing/selftests/vm/hmm-tests.c +83 -15

index 864f126ffd78..8eb81dfba4b3 100644
@@ -44,6 +44,14 @@ struct hmm_buffer {
 	int		fd;
 	uint64_t	cpages;
 	uint64_t	faults;
+	int		zone_device_type;
+};
+
+enum {
+	HMM_PRIVATE_DEVICE_ONE,
+	HMM_PRIVATE_DEVICE_TWO,
+	HMM_COHERENCE_DEVICE_ONE,
+	HMM_COHERENCE_DEVICE_TWO,
 };
 
 #define TWOMEG		(1 << 21)

@@ -60,6 +68,21 @@ FIXTURE(hmm)
 	unsigned int	page_shift;
 };
 
+FIXTURE_VARIANT(hmm)
+{
+	int     device_number;
+};
+
+FIXTURE_VARIANT_ADD(hmm, hmm_device_private)
+{
+	.device_number = HMM_PRIVATE_DEVICE_ONE,
+};
+
+FIXTURE_VARIANT_ADD(hmm, hmm_device_coherent)
+{
+	.device_number = HMM_COHERENCE_DEVICE_ONE,
+};
+
 FIXTURE(hmm2)
 {
 	int		fd0;

@@ -68,6 +91,24 @@ FIXTURE(hmm2)
 	unsigned int	page_shift;
 };
 
+FIXTURE_VARIANT(hmm2)
+{
+	int     device_number0;
+	int     device_number1;
+};
+
+FIXTURE_VARIANT_ADD(hmm2, hmm2_device_private)
+{
+	.device_number0 = HMM_PRIVATE_DEVICE_ONE,
+	.device_number1 = HMM_PRIVATE_DEVICE_TWO,
+};
+
+FIXTURE_VARIANT_ADD(hmm2, hmm2_device_coherent)
+{
+	.device_number0 = HMM_COHERENCE_DEVICE_ONE,
+	.device_number1 = HMM_COHERENCE_DEVICE_TWO,
+};
+
 static int hmm_open(int unit)
 {
 	char pathname[HMM_PATH_MAX];

@@ -81,12 +122,19 @@ static int hmm_open(int unit)
 	return fd;
 }
 
+static bool hmm_is_coherent_type(int dev_num)
+{
+	return (dev_num >= HMM_COHERENCE_DEVICE_ONE);
+}
+
 FIXTURE_SETUP(hmm)
 {
 	self->page_size = sysconf(_SC_PAGE_SIZE);
 	self->page_shift = ffs(self->page_size) - 1;
 
-	self->fd = hmm_open(0);
+	self->fd = hmm_open(variant->device_number);
+	if (self->fd < 0 && hmm_is_coherent_type(variant->device_number))
+		SKIP(exit(0), "DEVICE_COHERENT not available");
 	ASSERT_GE(self->fd, 0);
 }
 

@@ -95,9 +143,11 @@ FIXTURE_SETUP(hmm2)
 	self->page_size = sysconf(_SC_PAGE_SIZE);
 	self->page_shift = ffs(self->page_size) - 1;
 
-	self->fd0 = hmm_open(0);
+	self->fd0 = hmm_open(variant->device_number0);
+	if (self->fd0 < 0 && hmm_is_coherent_type(variant->device_number0))
+		SKIP(exit(0), "DEVICE_COHERENT not available");
 	ASSERT_GE(self->fd0, 0);
-	self->fd1 = hmm_open(1);
+	self->fd1 = hmm_open(variant->device_number1);
 	ASSERT_GE(self->fd1, 0);
 }
 

@@ -144,6 +194,7 @@ static int hmm_dmirror_cmd(int fd,
 	}
 	buffer->cpages = cmd.cpages;
 	buffer->faults = cmd.faults;
+	buffer->zone_device_type = cmd.zone_device_type;
 
 	return 0;
 }

@@ -211,6 +262,20 @@ static void hmm_nanosleep(unsigned int n)
 	nanosleep(&t, NULL);
 }
 
+static int hmm_migrate_sys_to_dev(int fd,
+				   struct hmm_buffer *buffer,
+				   unsigned long npages)
+{
+	return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_TO_DEV, buffer, npages);
+}
+
+static int hmm_migrate_dev_to_sys(int fd,
+				   struct hmm_buffer *buffer,
+				   unsigned long npages)
+{
+	return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_TO_SYS, buffer, npages);
+}
+
 /*
  * Simple NULL test of device open/close.
  */

@@ -875,7 +940,7 @@ TEST_F(hmm, migrate)
 		ptr[i] = i;
 
 	/* Migrate memory to device. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, npages);
 

@@ -923,7 +988,7 @@ TEST_F(hmm, migrate_fault)
 		ptr[i] = i;
 
 	/* Migrate memory to device. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, npages);
 

@@ -936,7 +1001,7 @@ TEST_F(hmm, migrate_fault)
 		ASSERT_EQ(ptr[i], i);
 
 	/* Migrate memory to the device again. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, npages);
 

@@ -976,7 +1041,7 @@ TEST_F(hmm, migrate_shared)
 	ASSERT_NE(buffer->ptr, MAP_FAILED);
 
 	/* Migrate memory to device. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
 	ASSERT_EQ(ret, -ENOENT);
 
 	hmm_buffer_free(buffer);

@@ -1015,7 +1080,7 @@ TEST_F(hmm2, migrate_mixed)
 	p = buffer->ptr;
 
 	/* Migrating a protected area should be an error. */
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, npages);
 	ASSERT_EQ(ret, -EINVAL);
 
 	/* Punch a hole after the first page address. */

@@ -1023,7 +1088,7 @@ TEST_F(hmm2, migrate_mixed)
 	ASSERT_EQ(ret, 0);
 
 	/* We expect an error if the vma doesn't cover the range. */
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 3);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 3);
 	ASSERT_EQ(ret, -EINVAL);
 
 	/* Page 2 will be a read-only zero page. */

@@ -1055,13 +1120,13 @@ TEST_F(hmm2, migrate_mixed)
 
 	/* Now try to migrate pages 2-5 to device 1. */
 	buffer->ptr = p + 2 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 4);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 4);
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, 4);
 
 	/* Page 5 won't be migrated to device 0 because it's on device 1. */
 	buffer->ptr = p + 5 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1);
+	ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1);
 	ASSERT_EQ(ret, -ENOENT);
 	buffer->ptr = p;
 

@@ -1070,8 +1135,12 @@ TEST_F(hmm2, migrate_mixed)
 }
 
 /*
- * Migrate anonymous memory to device private memory and fault it back to system
- * memory multiple times.
+ * Migrate anonymous memory to device memory and back to system memory
+ * multiple times. In case of private zone configuration, this is done
+ * through fault pages accessed by CPU. In case of coherent zone configuration,
+ * the pages from the device should be explicitly migrated back to system memory.
+ * The reason is Coherent device zone has coherent access by CPU, therefore
+ * it will not generate any page fault.
  */
 TEST_F(hmm, migrate_multiple)
 {

@@ -1107,8 +1176,7 @@ TEST_F(hmm, migrate_multiple)
 			ptr[i] = i;
 
 		/* Migrate memory to device. */
-		ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer,
-				      npages);
+		ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
 		ASSERT_EQ(ret, 0);
 		ASSERT_EQ(buffer->cpages, npages);
 

tools/testing/selftests/vm/hmm-tests.c +15 -5

+			ASSERT_EQ(ret, 0);
+		}
+
 		for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
 			ASSERT_EQ(ptr[i], i);
 

@@ -1312,13 +1385,13 @@ TEST_F(hmm2, snapshot)
 
 	/* Page 5 will be migrated to device 0. */
 	buffer->ptr = p + 5 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1);
+	ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1);
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, 1);
 
 	/* Page 6 will be migrated to device 1. */
 	buffer->ptr = p + 6 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 1);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 1);
 	ASSERT_EQ(ret, 0);
 	ASSERT_EQ(buffer->cpages, 1);
 

@@ -1335,9 +1408,16 @@ TEST_F(hmm2, snapshot)
 	ASSERT_EQ(m[2], HMM_DMIRROR_PROT_ZERO | HMM_DMIRROR_PROT_READ);
 	ASSERT_EQ(m[3], HMM_DMIRROR_PROT_READ);
 	ASSERT_EQ(m[4], HMM_DMIRROR_PROT_WRITE);
-	ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
-			HMM_DMIRROR_PROT_WRITE);
-	ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE);
+	if (!hmm_is_coherent_type(variant->device_number0)) {
+		ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
+				HMM_DMIRROR_PROT_WRITE);
+		ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE);
+	} else {
+		ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_COHERENT_LOCAL |
+				HMM_DMIRROR_PROT_WRITE);
+		ASSERT_EQ(m[6], HMM_DMIRROR_PROT_DEV_COHERENT_REMOTE |
+				HMM_DMIRROR_PROT_WRITE);
+	}
 
 	hmm_buffer_free(buffer);
 }

Quoted 6 lines · AEDT Alex Sierra

Test cases such as migrate_fault and migrate_multiple, were modified to explicit migrate from device to sys memory without the need of page faults, when using device coherent type.

Snapshot test case updated to read memory device type first and based on that, get the proper returned results migrate_ping_pong test case

Where is the migrate_ping_pong test? Did you perhaps forget to add it? :-)

Quoted 243 lines

added to test explicit migration from device to sys memory for both private and coherent zone types.

Helpers to migrate from device to sys memory and vicerversa were also added.

Signed-off-by Alex Sierra <[email protected]>

---
v2:
Set FIXTURE_VARIANT to add multiple device types to the FIXTURE. This will run all the tests for each device type (private and coherent) in case both existed during hmm-test driver probed.

---
  tools/testing/selftests/vm/hmm-tests.c | 122 ++++++++++++++++++++-----
  1 file changed, 101 insertions(+), 21 deletions(-)

tools/testing/selftests/vm/hmm-tests.c +83 -15

index 864f126ffd78..8eb81dfba4b3 100644
@@ -44,6 +44,14 @@ struct hmm_buffer {
  	int		fd;
  	uint64_t	cpages;
  	uint64_t	faults;
+	int		zone_device_type;
+};
+
+enum {
+	HMM_PRIVATE_DEVICE_ONE,
+	HMM_PRIVATE_DEVICE_TWO,
+	HMM_COHERENCE_DEVICE_ONE,
+	HMM_COHERENCE_DEVICE_TWO,
  };
 
  #define TWOMEG		(1 << 21)

@@ -60,6 +68,21 @@ FIXTURE(hmm)
  	unsigned int	page_shift;
  };
 
+FIXTURE_VARIANT(hmm)
+{
+	int     device_number;
+};
+
+FIXTURE_VARIANT_ADD(hmm, hmm_device_private)
+{
+	.device_number = HMM_PRIVATE_DEVICE_ONE,
+};
+
+FIXTURE_VARIANT_ADD(hmm, hmm_device_coherent)
+{
+	.device_number = HMM_COHERENCE_DEVICE_ONE,
+};
+
  FIXTURE(hmm2)
  {
  	int		fd0;

@@ -68,6 +91,24 @@ FIXTURE(hmm2)
  	unsigned int	page_shift;
  };
 
+FIXTURE_VARIANT(hmm2)
+{
+	int     device_number0;
+	int     device_number1;
+};
+
+FIXTURE_VARIANT_ADD(hmm2, hmm2_device_private)
+{
+	.device_number0 = HMM_PRIVATE_DEVICE_ONE,
+	.device_number1 = HMM_PRIVATE_DEVICE_TWO,
+};
+
+FIXTURE_VARIANT_ADD(hmm2, hmm2_device_coherent)
+{
+	.device_number0 = HMM_COHERENCE_DEVICE_ONE,
+	.device_number1 = HMM_COHERENCE_DEVICE_TWO,
+};
+
  static int hmm_open(int unit)
  {
  	char pathname[HMM_PATH_MAX];

@@ -81,12 +122,19 @@ static int hmm_open(int unit)
  	return fd;
  }
 
+static bool hmm_is_coherent_type(int dev_num)
+{
+	return (dev_num >= HMM_COHERENCE_DEVICE_ONE);
+}
+
  FIXTURE_SETUP(hmm)
  {
  	self->page_size = sysconf(_SC_PAGE_SIZE);
  	self->page_shift = ffs(self->page_size) - 1;
 
-	self->fd = hmm_open(0);
+	self->fd = hmm_open(variant->device_number);
+	if (self->fd < 0 && hmm_is_coherent_type(variant->device_number))
+		SKIP(exit(0), "DEVICE_COHERENT not available");
  	ASSERT_GE(self->fd, 0);
  }
 

@@ -95,9 +143,11 @@ FIXTURE_SETUP(hmm2)
  	self->page_size = sysconf(_SC_PAGE_SIZE);
  	self->page_shift = ffs(self->page_size) - 1;
 
-	self->fd0 = hmm_open(0);
+	self->fd0 = hmm_open(variant->device_number0);
+	if (self->fd0 < 0 && hmm_is_coherent_type(variant->device_number0))
+		SKIP(exit(0), "DEVICE_COHERENT not available");
  	ASSERT_GE(self->fd0, 0);
-	self->fd1 = hmm_open(1);
+	self->fd1 = hmm_open(variant->device_number1);
  	ASSERT_GE(self->fd1, 0);
  }
 

@@ -144,6 +194,7 @@ static int hmm_dmirror_cmd(int fd,
  	}
  	buffer->cpages = cmd.cpages;
  	buffer->faults = cmd.faults;
+	buffer->zone_device_type = cmd.zone_device_type;
 
  	return 0;
  }

@@ -211,6 +262,20 @@ static void hmm_nanosleep(unsigned int n)
  	nanosleep(&t, NULL);
  }
 
+static int hmm_migrate_sys_to_dev(int fd,
+				   struct hmm_buffer *buffer,
+				   unsigned long npages)
+{
+	return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_TO_DEV, buffer, npages);
+}
+
+static int hmm_migrate_dev_to_sys(int fd,
+				   struct hmm_buffer *buffer,
+				   unsigned long npages)
+{
+	return hmm_dmirror_cmd(fd, HMM_DMIRROR_MIGRATE_TO_SYS, buffer, npages);
+}
+
  /*
   * Simple NULL test of device open/close.
   */

@@ -875,7 +940,7 @@ TEST_F(hmm, migrate)
  		ptr[i] = i;
 
  	/* Migrate memory to device. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
  	ASSERT_EQ(ret, 0);
  	ASSERT_EQ(buffer->cpages, npages);
 

@@ -923,7 +988,7 @@ TEST_F(hmm, migrate_fault)
  		ptr[i] = i;
 
  	/* Migrate memory to device. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
  	ASSERT_EQ(ret, 0);
  	ASSERT_EQ(buffer->cpages, npages);
 

@@ -936,7 +1001,7 @@ TEST_F(hmm, migrate_fault)
  		ASSERT_EQ(ptr[i], i);
 
  	/* Migrate memory to the device again. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
  	ASSERT_EQ(ret, 0);
  	ASSERT_EQ(buffer->cpages, npages);
 

@@ -976,7 +1041,7 @@ TEST_F(hmm, migrate_shared)
  	ASSERT_NE(buffer->ptr, MAP_FAILED);
 
  	/* Migrate memory to device. */
-	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
  	ASSERT_EQ(ret, -ENOENT);
 
  	hmm_buffer_free(buffer);

@@ -1015,7 +1080,7 @@ TEST_F(hmm2, migrate_mixed)
  	p = buffer->ptr;
 
  	/* Migrating a protected area should be an error. */
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, npages);
  	ASSERT_EQ(ret, -EINVAL);
 
  	/* Punch a hole after the first page address. */

@@ -1023,7 +1088,7 @@ TEST_F(hmm2, migrate_mixed)
  	ASSERT_EQ(ret, 0);
 
  	/* We expect an error if the vma doesn't cover the range. */
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 3);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 3);
  	ASSERT_EQ(ret, -EINVAL);
 
  	/* Page 2 will be a read-only zero page. */

@@ -1055,13 +1120,13 @@ TEST_F(hmm2, migrate_mixed)
 
  	/* Now try to migrate pages 2-5 to device 1. */
  	buffer->ptr = p + 2 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 4);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 4);
  	ASSERT_EQ(ret, 0);
  	ASSERT_EQ(buffer->cpages, 4);
 
  	/* Page 5 won't be migrated to device 0 because it's on device 1. */
  	buffer->ptr = p + 5 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1);
+	ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1);
  	ASSERT_EQ(ret, -ENOENT);
  	buffer->ptr = p;
 

@@ -1070,8 +1135,12 @@ TEST_F(hmm2, migrate_mixed)
  }
 
  /*
- * Migrate anonymous memory to device private memory and fault it back to system
- * memory multiple times.
+ * Migrate anonymous memory to device memory and back to system memory
+ * multiple times. In case of private zone configuration, this is done
+ * through fault pages accessed by CPU. In case of coherent zone configuration,
+ * the pages from the device should be explicitly migrated back to system memory.
+ * The reason is Coherent device zone has coherent access by CPU, therefore
+ * it will not generate any page fault.
   */
  TEST_F(hmm, migrate_multiple)
  {

@@ -1107,8 +1176,7 @@ TEST_F(hmm, migrate_multiple)
  			ptr[i] = i;
 
  		/* Migrate memory to device. */
-		ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer,
-				      npages);
+		ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
  		ASSERT_EQ(ret, 0);
  		ASSERT_EQ(buffer->cpages, npages);
 

tools/testing/selftests/vm/hmm-tests.c TEST_F(hmm, migrate_multiple) · line 1189

Quoted 7 lines

tools/testing/selftests/vm/hmm-tests.c +3 -1

@@ -1116,7 +1184,12 @@ TEST_F(hmm, migrate_multiple)
  		for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
  			ASSERT_EQ(ptr[i], i);
 
-		/* Fault pages back to system memory and check them. */
+		/* Migrate back to system memory and check them. */
+		if (hmm_is_coherent_type(variant->device_number)) {
+			ret = hmm_migrate_dev_to_sys(self->fd, buffer, npages);

So I think this will still pass even if nothing migrates so as mentioned on the previous patch I think we need to check for the number of pages that actually migrated. Alternatively I suppose you could do a snapshot and check that, but that seems like it would be harder. Otherwise I think this looks good.

Quoted 43 lines

tools/testing/selftests/vm/hmm-tests.c +15 -5

+			ASSERT_EQ(ret, 0);
+		}
+
  		for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
  			ASSERT_EQ(ptr[i], i);
 

@@ -1312,13 +1385,13 @@ TEST_F(hmm2, snapshot)
 
  	/* Page 5 will be migrated to device 0. */
  	buffer->ptr = p + 5 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd0, HMM_DMIRROR_MIGRATE, buffer, 1);
+	ret = hmm_migrate_sys_to_dev(self->fd0, buffer, 1);
  	ASSERT_EQ(ret, 0);
  	ASSERT_EQ(buffer->cpages, 1);
 
  	/* Page 6 will be migrated to device 1. */
  	buffer->ptr = p + 6 * self->page_size;
-	ret = hmm_dmirror_cmd(self->fd1, HMM_DMIRROR_MIGRATE, buffer, 1);
+	ret = hmm_migrate_sys_to_dev(self->fd1, buffer, 1);
  	ASSERT_EQ(ret, 0);
  	ASSERT_EQ(buffer->cpages, 1);
 

@@ -1335,9 +1408,16 @@ TEST_F(hmm2, snapshot)
  	ASSERT_EQ(m[2], HMM_DMIRROR_PROT_ZERO | HMM_DMIRROR_PROT_READ);
  	ASSERT_EQ(m[3], HMM_DMIRROR_PROT_READ);
  	ASSERT_EQ(m[4], HMM_DMIRROR_PROT_WRITE);
-	ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
-			HMM_DMIRROR_PROT_WRITE);
-	ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE);
+	if (!hmm_is_coherent_type(variant->device_number0)) {
+		ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
+				HMM_DMIRROR_PROT_WRITE);
+		ASSERT_EQ(m[6], HMM_DMIRROR_PROT_NONE);
+	} else {
+		ASSERT_EQ(m[5], HMM_DMIRROR_PROT_DEV_COHERENT_LOCAL |
+				HMM_DMIRROR_PROT_WRITE);
+		ASSERT_EQ(m[6], HMM_DMIRROR_PROT_DEV_COHERENT_REMOTE |
+				HMM_DMIRROR_PROT_WRITE);
+	}
 
  	hmm_buffer_free(buffer);
  }

Add two more parameters to set spm_addr_dev0 & spm_addr_dev1 addresses. These two parameters configure the start SP addresses for each device in test_hmm driver. Consequently, this configures zone device type as coherent.

Signed-off-by Alex Sierra <[email protected]>

---
v2:
Add more mknods for device coherent type. These are represented under /dev/hmm_mirror2 and /dev/hmm_mirror3, only in case they have created at probing the hmm-test driver.

---
 tools/testing/selftests/vm/test_hmm.sh | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

tools/testing/selftests/vm/test_hmm.sh +21 -3

index 0647b525a625..539c9371e592 100755
@@ -40,11 +40,26 @@ check_test_requirements()
 
 load_driver()
 {
-	modprobe $DRIVER > /dev/null 2>&1
+	if [ $# -eq 0 ]; then
+		modprobe $DRIVER > /dev/null 2>&1
+	else
+		if [ $# -eq 2 ]; then
+			modprobe $DRIVER spm_addr_dev0=$1 spm_addr_dev1=$2
+				> /dev/null 2>&1
+		else
+			echo "Missing module parameters. Make sure pass"\
+			"spm_addr_dev0 and spm_addr_dev1"
+			usage
+		fi
+	fi
 	if [ $? == 0 ]; then
 		major=$(awk "\$2==\"HMM_DMIRROR\" {print \$1}" /proc/devices)
 		mknod /dev/hmm_dmirror0 c $major 0
 		mknod /dev/hmm_dmirror1 c $major 1
+		if [ $# -eq 2 ]; then
+			mknod /dev/hmm_dmirror2 c $major 2
+			mknod /dev/hmm_dmirror3 c $major 3
+		fi
 	fi
 }
 

@@ -58,7 +73,7 @@ run_smoke()
 {
 	echo "Running smoke test. Note, this test provides basic coverage."
 
-	load_driver
+	load_driver $1 $2
 	$(dirname "${BASH_SOURCE[0]}")/hmm-tests
 	unload_driver
 }

@@ -75,6 +90,9 @@ usage()
 	echo "# Smoke testing"
 	echo "./${TEST_NAME}.sh smoke"
 	echo
+	echo "# Smoke testing with SPM enabled"
+	echo "./${TEST_NAME}.sh smoke <spm_addr_dev0> <spm_addr_dev1>"
+	echo
 	exit 0
 }
 

@@ -84,7 +102,7 @@ function run_test()
 		usage
 	else
 		if [ "$1" = "smoke" ]; then
-			run_smoke
+			run_smoke $2 $3
 		else
 			usage
 		fi

This patch series introduces MEMORY_DEVICE_COHERENT, a type of memory owned by a device that can be mapped into CPU page tables like MEMORY_DEVICE_GENERIC and can also be migrated like MEMORY_DEVICE_PRIVATE.

Christoph, the suggestion to incorporate Ralph Campbell’s refcount cleanup patch into our hardware page migration patchset originally came from you, but it proved impractical to do things in that order because the refcount cleanup introduced a bug with wide ranging structural implications. Instead, we amended Ralph’s patch so that it could be applied after merging the migration work. As we saw from the recent discussion, merging the refcount work is going to take some time and cooperation between multiple development groups, while the migration work is ready now and is needed now. So we propose to merge this patchset first and continue to work with Ralph and others to merge the refcount cleanup separately, when it is ready.

This patch series is mostly self-contained except for a few places where it needs to update other subsystems to handle the new memory type. System stability and performance are not affected according to our ongoing testing, including xfstests.

How it works: The system BIOS advertises the GPU device memory (aka VRAM) as SPM (special purpose memory) in the UEFI system address map.

The amdgpu driver registers the memory with devmap as MEMORY_DEVICE_COHERENT using devm_memremap_pages. The initial user for this hardware page migration capability is the Frontier supercomputer project. This functionality is not AMD-specific. We expect other GPU vendors to find this functionality useful, and possibly other hardware types in the future.

Our test nodes in the lab are similar to the Frontier configuration, with .5 TB of system memory plus 256 GB of device memory split across 4 GPUs, all in a single coherent address space. Page migration is expected to improve application efficiency significantly. We will report empirical results as they become available.

We extended hmm_test to cover migration of MEMORY_DEVICE_COHERENT. This patch set builds on HMM and our SVM memory manager already merged in 5.15.

v2:
- test_hmm is now able to create private and coherent device mirror instances in the same driver probe. This adds more usability to the hmm test by not having to remove the kernel module for each device type test (private/coherent type). This is done by passing the module parameters spm_addr_dev0 & spm_addr_dev1. In this case, it will create four instances of device_mirror. The first two correspond to private device type, the last two to coherent type. Then, they can be easily accessed from user space through /dev/hmm_mirror<num_device>. Usually num_device 0 and 1 are for private, and 2 and 3 for coherent types.

- Coherent device type pages at gup are now migrated back to system memory if they have been long term pinned (FOLL_LONGTERM). The reason is these pages could eventually interfere with their own device memory manager. A new hmm_gup_test has been added to the hmm-test to test this functionality. It makes use of the gup_test module to long term pin user pages that have been migrate to device memory first.

- Other patch corrections made by Felix, Alistair and Christoph.

v3:
- Based on last v2 feedback we got from Alistair, we've decided to remove migration logic for FOLL_LONGTERM coherent device type pages at gup for now. Ideally, this should be done through the kernel mm, instead of calling the device driver to do it. Currently, there's no support for migrating device pages based on pfn, mainly because migrate_pages() relies on pages being LRU pages. Alistair mentioned, he has started to work on adding this migrate device pages logic. For now, we fail on get_user_pages call with FOLL_LONGTERM for DEVICE_COHERENT pages.

- Also, hmm_gup_test has been removed from hmm-test. We plan to include it again after this migration work is ready.

- Addressed Liam Howlett's feedback changes.

Alex Sierra (10):
mm: add zone device coherent type memory support
mm: add device coherent vma selection for memory migration mm/gup: fail get_user_pages for LONGTERM dev coherent type drm/amdkfd: add SPM support for SVM
drm/amdkfd: coherent type as sys mem on migration to ram
lib: test_hmm add ioctl to get zone device type
lib: test_hmm add module param for zone device type
lib: add support for device coherent type in test_hmm
tools: update hmm-test to support device coherent type
tools: update test_hmm script to support SP config

 drivers/gpu/drm/amd/amdkfd/kfd_migrate.c |  34 ++-
 include/linux/memremap.h                 |   8 +
 include/linux/migrate.h                  |   1 +
 include/linux/mm.h                       |  16 ++
 lib/test_hmm.c                           | 333 +++++++++++++++++------
 lib/test_hmm_uapi.h                      |  22 +-
 mm/gup.c                                 |   7 +
 mm/memcontrol.c                          |   6 +-
 mm/memory-failure.c                      |   8 +-
 mm/memremap.c                            |   5 +-
 mm/migrate.c                             |  30 +-
 tools/testing/selftests/vm/hmm-tests.c   | 122 +++++++--
 tools/testing/selftests/vm/test_hmm.sh   |  24 +-
 13 files changed, 475 insertions(+), 141 deletions(-)

I have been looking at this in relation to the migration code and noticed we have the following in try_to_migrate():

        if (is_zone_device_page(page) && !is_device_private_page(page))
                return;

Which if I'm understanding correctly means that migration of device coherent pages will always fail. Given that I do wonder how hmm-tests are passing, but I assume you must always be hitting this fast path in migrate_vma_collect_pmd():

/*
* Optimize for the common case where page is only mapped once
* in one process. If we can lock the page, then we can safely
* set up a special migration page table entry now. */

Meaning that try_to_migrate() never gets called from migrate_vma_unmap(). So you will also need some changes to try_to_migrate() and possibly try_to_migrate_one() to make this reliable.

This patch series introduces MEMORY_DEVICE_COHERENT, a type of memory owned by a device that can be mapped into CPU page tables like MEMORY_DEVICE_GENERIC and can also be migrated like MEMORY_DEVICE_PRIVATE.

Christoph, the suggestion to incorporate Ralph Campbell’s refcount cleanup patch into our hardware page migration patchset originally came from you, but it proved impractical to do things in that order because the refcount cleanup introduced a bug with wide ranging structural implications. Instead, we amended Ralph’s patch so that it could be applied after merging the migration work. As we saw from the recent discussion, merging the refcount work is going to take some time and cooperation between multiple development groups, while the migration work is ready now and is needed now. So we propose to merge this patchset first and continue to work with Ralph and others to merge the refcount cleanup separately, when it is ready.

This patch series is mostly self-contained except for a few places where it needs to update other subsystems to handle the new memory type. System stability and performance are not affected according to our ongoing testing, including xfstests.

How it works: The system BIOS advertises the GPU device memory (aka VRAM) as SPM (special purpose memory) in the UEFI system address map.

The amdgpu driver registers the memory with devmap as MEMORY_DEVICE_COHERENT using devm_memremap_pages. The initial user for this hardware page migration capability is the Frontier supercomputer project. This functionality is not AMD-specific. We expect other GPU vendors to find this functionality useful, and possibly other hardware types in the future.

Our test nodes in the lab are similar to the Frontier configuration, with .5 TB of system memory plus 256 GB of device memory split across 4 GPUs, all in a single coherent address space. Page migration is expected to improve application efficiency significantly. We will report empirical results as they become available.

Quoted 33 lines

This patch series introduces MEMORY_DEVICE_COHERENT, a type of memory owned by a device that can be mapped into CPU page tables like MEMORY_DEVICE_GENERIC and can also be migrated like MEMORY_DEVICE_PRIVATE.

Christoph, the suggestion to incorporate Ralph Campbell’s refcount cleanup patch into our hardware page migration patchset originally came from you, but it proved impractical to do things in that order because the refcount cleanup introduced a bug with wide ranging structural implications. Instead, we amended Ralph’s patch so that it could be applied after merging the migration work. As we saw from the recent discussion, merging the refcount work is going to take some time and cooperation between multiple development groups, while the migration work is ready now and is needed now. So we propose to merge this patchset first and continue to work with Ralph and others to merge the refcount cleanup separately, when it is ready.

This patch series is mostly self-contained except for a few places where it needs to update other subsystems to handle the new memory type. System stability and performance are not affected according to our ongoing testing, including xfstests.

How it works: The system BIOS advertises the GPU device memory (aka VRAM) as SPM (special purpose memory) in the UEFI system address map.

The amdgpu driver registers the memory with devmap as MEMORY_DEVICE_COHERENT using devm_memremap_pages. The initial user for this hardware page migration capability is the Frontier supercomputer project. This functionality is not AMD-specific. We expect other GPU vendors to find this functionality useful, and possibly other hardware types in the future.

Quoted 5 lines

Our test nodes in the lab are similar to the Frontier configuration, with .5 TB of system memory plus 256 GB of device memory split across 4 GPUs, all in a single coherent address space. Page migration is expected to improve application efficiency significantly. We will report empirical results as they become available.

Hi,

might be a dumb question because I'm not too familiar with MEMORY_DEVICE_COHERENT, but who's in charge of migrating *to* that memory? Or how does a process ever get a grab on such pages?

And where does migration come into play? I assume migration is only required to migrate off of that device memory to ordinary system RAM when required because the device memory has to be freed up, correct?

(a high level description on how this is exploited from users space would be great)