Nouveau - Jul 2020 - [PATCH v3 0/5] mm/migrate: avoid device private invalidations

The goal for this series is to avoid device private memory TLB
invalidations when migrating a range of addresses from system
memory to device private memory and some of those pages have already
been migrated. The approach taken is to introduce a new mmu notifier
invalidation event type and use that in the device driver to skip
invalidation callbacks from migrate_vma_setup(). The device driver is
also then expected to handle device MMU invalidations as part of the
migrate_vma_setup(), migrate_vma_pages(), migrate_vma_finalize() process.
Note that this is opt-in. A device driver can simply invalidate its MMU
in the mmu notifier callback and not handle MMU invalidations in the
migration sequence.

This series is based on Jason Gunthorpe's HMM tree (linux-5.8.0-rc4).

Also, this replaces the need for the following two patches I sent:
("mm: fix migrate_vma_setup() src_owner and normal pages")
https://lore.kernel.org/linux-mm/20200622222008.9971-1-rcampbell at nvidia.com
("nouveau: fix mixed normal and device private page migration")
https://lore.kernel.org/lkml/20200622233854.10889-3-rcampbell at nvidia.com

Bharata Rao, let me know if I can add your reviewed-by back since
I made a fair number of changes to this version of the series.

Changes in v3:
Changed the direction field "dir" to a "flags" field and
renamed
  src_owner to pgmap_owner.
Fixed a locking issue in nouveau for the migration invalidation.
Added a HMM selftest test case to exercise the HMM test driver
  invalidation changes.
Removed reviewed-by Bharata B Rao since this version is moderately
  changed.

Changes in v2:
Rebase to Jason Gunthorpe's HMM tree.
Added reviewed-by from Bharata B Rao.
Rename the mmu_notifier_range::data field to migrate_pgmap_owner as
  suggested by Jason Gunthorpe.

Ralph Campbell (5):
  nouveau: fix storing invalid ptes
  mm/migrate: add a flags parameter to migrate_vma
  mm/notifier: add migration invalidation type
  nouveau/svm: use the new migration invalidation
  mm/hmm/test: use the new migration invalidation

 arch/powerpc/kvm/book3s_hv_uvmem.c            |  4 ++-
 drivers/gpu/drm/nouveau/nouveau_dmem.c        | 19 ++++++++---
 drivers/gpu/drm/nouveau/nouveau_svm.c         | 21 +++++-------
 drivers/gpu/drm/nouveau/nouveau_svm.h         | 13 ++++++-
 .../drm/nouveau/nvkm/subdev/mmu/vmmgp100.c    | 13 ++++---
 include/linux/migrate.h                       | 16 ++++++---
 include/linux/mmu_notifier.h                  |  7 ++++
 lib/test_hmm.c                                | 34 +++++++++++--------
 mm/migrate.c                                  | 14 ++++++--
 tools/testing/selftests/vm/hmm-tests.c        | 18 +++++++---
 10 files changed, 112 insertions(+), 47 deletions(-)

-- 
2.20.1

When migrating a range of system memory to device private memory, some
of the pages in the address range may not be migrating. In this case,
the non migrating pages won't have a new GPU MMU entry to store but
the nvif_object_ioctl() NVIF_VMM_V0_PFNMAP method doesn't check the input
and stores a bad valid GPU page table entry.
Fix this by skipping the invalid input PTEs when updating the GPU page
tables.

Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
---
 drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c
b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c
index ed37fddd063f..7eabe9fe0d2b 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/mmu/vmmgp100.c
@@ -79,8 +79,12 @@ gp100_vmm_pgt_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt
*pt,
 	dma_addr_t addr;
 
 	nvkm_kmap(pt->memory);
-	while (ptes--) {
+	for (; ptes; ptes--, map->pfn++) {
 		u64 data = 0;
+
+		if (!(*map->pfn & NVKM_VMM_PFN_V))
+			continue;
+
 		if (!(*map->pfn & NVKM_VMM_PFN_W))
 			data |= BIT_ULL(6); /* RO. */
 
@@ -100,7 +104,6 @@ gp100_vmm_pgt_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt
*pt,
 		}
 
 		VMM_WO064(pt, vmm, ptei++ * 8, data);
-		map->pfn++;
 	}
 	nvkm_done(pt->memory);
 }
@@ -310,9 +313,12 @@ gp100_vmm_pd0_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt
*pt,
 	dma_addr_t addr;
 
 	nvkm_kmap(pt->memory);
-	while (ptes--) {
+	for (; ptes; ptes--, map->pfn++) {
 		u64 data = 0;
 
+		if (!(*map->pfn & NVKM_VMM_PFN_V))
+			continue;
+
 		if (!(*map->pfn & NVKM_VMM_PFN_W))
 			data |= BIT_ULL(6); /* RO. */
 
@@ -332,7 +338,6 @@ gp100_vmm_pd0_pfn(struct nvkm_vmm *vmm, struct nvkm_mmu_pt
*pt,
 		}
 
 		VMM_WO064(pt, vmm, ptei++ * 16, data);
-		map->pfn++;
 	}
 	nvkm_done(pt->memory);
 }
-- 
2.20.1

The src_owner field in struct migrate_vma is being used for two purposes,
it acts as a selection filter for which types of pages are to be migrated
and it identifies device private pages owned by the caller. Split this
into separate parameters so the src_owner field can be used just to
identify device private pages owned by the caller of migrate_vma_setup().
Rename the src_owner field to pgmap_owner to reflect it is now used only
to identify which device private pages to migrate.

Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
---
 arch/powerpc/kvm/book3s_hv_uvmem.c     |  4 +++-
 drivers/gpu/drm/nouveau/nouveau_dmem.c |  4 +++-
 include/linux/migrate.h                | 13 +++++++++----
 lib/test_hmm.c                         |  6 ++++--
 mm/migrate.c                           |  6 ++++--
 5 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c
b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 09d8119024db..6850bd04bcb9 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -400,6 +400,7 @@ kvmppc_svm_page_in(struct vm_area_struct *vma, unsigned long
start,
 	mig.end = end;
 	mig.src = &src_pfn;
 	mig.dst = &dst_pfn;
+	mig.flags = MIGRATE_VMA_SELECT_SYSTEM;
 
 	/*
 	 * We come here with mmap_lock write lock held just for
@@ -577,7 +578,8 @@ kvmppc_svm_page_out(struct vm_area_struct *vma, unsigned
long start,
 	mig.end = end;
 	mig.src = &src_pfn;
 	mig.dst = &dst_pfn;
-	mig.src_owner = &kvmppc_uvmem_pgmap;
+	mig.pgmap_owner = &kvmppc_uvmem_pgmap;
+	mig.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;
 
 	mutex_lock(&kvm->arch.uvmem_lock);
 	/* The requested page is already paged-out, nothing to do */
diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index e5c230d9ae24..78b9e3c2a5b3 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -182,7 +182,8 @@ static vm_fault_t nouveau_dmem_migrate_to_ram(struct
vm_fault *vmf)
 		.end		= vmf->address + PAGE_SIZE,
 		.src		= &src,
 		.dst		= &dst,
-		.src_owner	= drm->dev,
+		.pgmap_owner	= drm->dev,
+		.flags		= MIGRATE_VMA_SELECT_DEVICE_PRIVATE,
 	};
 
 	/*
@@ -615,6 +616,7 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
 	struct migrate_vma args = {
 		.vma		= vma,
 		.start		= start,
+		.flags		= MIGRATE_VMA_SELECT_SYSTEM,
 	};
 	unsigned long i;
 	u64 *pfns;
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 3e546cbf03dd..aafec0ca7b41 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -180,6 +180,11 @@ static inline unsigned long migrate_pfn(unsigned long pfn)
 	return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID;
 }
 
+enum migrate_vma_direction {
+	MIGRATE_VMA_SELECT_SYSTEM         = (1UL << 0),
+	MIGRATE_VMA_SELECT_DEVICE_PRIVATE = (1UL << 1),
+};
+
 struct migrate_vma {
 	struct vm_area_struct	*vma;
 	/*
@@ -199,11 +204,11 @@ struct migrate_vma {
 
 	/*
 	 * Set to the owner value also stored in page->pgmap->owner for
-	 * migrating out of device private memory.  If set only device
-	 * private pages with this owner are migrated.  If not set
-	 * device private pages are not migrated at all.
+	 * migrating out of device private memory. The flags also need to
+	 * be set to MIGRATE_VMA_SELECT_DEVICE_PRIVATE.
 	 */
-	void			*src_owner;
+	void			*pgmap_owner;
+	unsigned long		flags;
 };
 
 int migrate_vma_setup(struct migrate_vma *args);
diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 9aa577afc269..74c6ee66ef15 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -702,7 +702,8 @@ static int dmirror_migrate(struct dmirror *dmirror,
 		args.dst = dst_pfns;
 		args.start = addr;
 		args.end = next;
-		args.src_owner = NULL;
+		args.pgmap_owner = NULL;
+		args.flags = MIGRATE_VMA_SELECT_SYSTEM;
 		ret = migrate_vma_setup(&args);
 		if (ret)
 			goto out;
@@ -1053,7 +1054,8 @@ static vm_fault_t dmirror_devmem_fault(struct vm_fault
*vmf)
 	args.end = args.start + PAGE_SIZE;
 	args.src = &src_pfns;
 	args.dst = &dst_pfns;
-	args.src_owner = dmirror->mdevice;
+	args.pgmap_owner = dmirror->mdevice;
+	args.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;
 
 	if (migrate_vma_setup(&args))
 		return VM_FAULT_SIGBUS;
diff --git a/mm/migrate.c b/mm/migrate.c
index f37729673558..e3ea68e3a08b 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2287,7 +2287,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 				goto next;
 
 			page = device_private_entry_to_page(entry);
-			if (page->pgmap->owner != migrate->src_owner)
+			if (!(migrate->flags &
+				MIGRATE_VMA_SELECT_DEVICE_PRIVATE) ||
+			    page->pgmap->owner != migrate->pgmap_owner)
 				goto next;
 
 			mpfn = migrate_pfn(page_to_pfn(page)) |
@@ -2295,7 +2297,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
 			if (is_write_device_private_entry(entry))
 				mpfn |= MIGRATE_PFN_WRITE;
 		} else {
-			if (migrate->src_owner)
+			if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
 				goto next;
 			pfn = pte_pfn(pte);
 			if (is_zero_pfn(pfn)) {
-- 
2.20.1

Currently migrate_vma_setup() calls mmu_notifier_invalidate_range_start()
which flushes all device private page mappings whether or not a page
is being migrated to/from device private memory. In order to not disrupt
device mappings that are not being migrated, shift the responsibility
for clearing device private mappings to the device driver and leave
CPU page table unmapping handled by migrate_vma_setup(). To support
this, the caller of migrate_vma_setup() should always set struct
migrate_vma::pgmap_owner to a non NULL value that matches the device
private page->pgmap->owner. This value is then passed to the struct
mmu_notifier_range with a new event type which the driver's invalidation
function can use to avoid device MMU invalidations.

Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
---
 include/linux/migrate.h      | 3 +++
 include/linux/mmu_notifier.h | 7 +++++++
 mm/migrate.c                 | 8 +++++++-
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index aafec0ca7b41..4cc7097d0271 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -206,6 +206,9 @@ struct migrate_vma {
 	 * Set to the owner value also stored in page->pgmap->owner for
 	 * migrating out of device private memory. The flags also need to
 	 * be set to MIGRATE_VMA_SELECT_DEVICE_PRIVATE.
+	 * The caller should always set this field when using mmu notifier
+	 * callbacks to avoid device MMU invalidations for device private
+	 * pages that are not being migrated.
 	 */
 	void			*pgmap_owner;
 	unsigned long		flags;
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index fc68f3570e19..1921fcf6be5b 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -38,6 +38,10 @@ struct mmu_interval_notifier;
  *
  * @MMU_NOTIFY_RELEASE: used during mmu_interval_notifier invalidate to signal
  * that the mm refcount is zero and the range is no longer accessible.
+ *
+ * @MMU_NOTIFY_MIGRATE: used during migrate_vma_collect() invalidate to signal
+ * a device driver to possibly ignore the invalidation if the
+ * migrate_pgmap_owner field matches the driver's device private pgmap
owner.
  */
 enum mmu_notifier_event {
 	MMU_NOTIFY_UNMAP = 0,
@@ -46,6 +50,7 @@ enum mmu_notifier_event {
 	MMU_NOTIFY_PROTECTION_PAGE,
 	MMU_NOTIFY_SOFT_DIRTY,
 	MMU_NOTIFY_RELEASE,
+	MMU_NOTIFY_MIGRATE,
 };
 
 #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
@@ -264,6 +269,7 @@ struct mmu_notifier_range {
 	unsigned long end;
 	unsigned flags;
 	enum mmu_notifier_event event;
+	void *migrate_pgmap_owner;
 };
 
 static inline int mm_has_notifiers(struct mm_struct *mm)
@@ -513,6 +519,7 @@ static inline void mmu_notifier_range_init(struct
mmu_notifier_range *range,
 	range->start = start;
 	range->end = end;
 	range->flags = flags;
+	range->migrate_pgmap_owner = NULL;
 }
 
 #define ptep_clear_flush_young_notify(__vma, __address, __ptep)		\
diff --git a/mm/migrate.c b/mm/migrate.c
index e3ea68e3a08b..96e1f41a991e 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2392,8 +2392,14 @@ static void migrate_vma_collect(struct migrate_vma
*migrate)
 {
 	struct mmu_notifier_range range;
 
-	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL,
+	/*
+	 * Note that the pgmap_owner is passed to the mmu notifier callback so
+	 * that the registered device driver can skip invalidating device
+	 * private page mappings that won't be migrated.
+	 */
+	mmu_notifier_range_init(&range, MMU_NOTIFY_MIGRATE, 0, migrate->vma,
 			migrate->vma->vm_mm, migrate->start, migrate->end);
+	range.migrate_pgmap_owner = migrate->pgmap_owner;
 	mmu_notifier_invalidate_range_start(&range);
 
 	walk_page_range(migrate->vma->vm_mm, migrate->start, migrate->end,
-- 
2.20.1

Use the new MMU_NOTIFY_MIGRATE event to skip GPU MMU invalidations of
device private memory and handle the invalidation in the driver as part
of migrating device private memory.

Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
---
 drivers/gpu/drm/nouveau/nouveau_dmem.c | 15 ++++++++++++---
 drivers/gpu/drm/nouveau/nouveau_svm.c  | 21 +++++++++------------
 drivers/gpu/drm/nouveau/nouveau_svm.h  | 13 ++++++++++++-
 3 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_dmem.c
b/drivers/gpu/drm/nouveau/nouveau_dmem.c
index 78b9e3c2a5b3..511fe04cd680 100644
--- a/drivers/gpu/drm/nouveau/nouveau_dmem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_dmem.c
@@ -140,6 +140,7 @@ static vm_fault_t nouveau_dmem_fault_copy_one(struct
nouveau_drm *drm,
 {
 	struct device *dev = drm->dev->dev;
 	struct page *dpage, *spage;
+	struct nouveau_svmm *svmm;
 
 	spage = migrate_pfn_to_page(args->src[0]);
 	if (!spage || !(args->src[0] & MIGRATE_PFN_MIGRATE))
@@ -154,14 +155,19 @@ static vm_fault_t nouveau_dmem_fault_copy_one(struct
nouveau_drm *drm,
 	if (dma_mapping_error(dev, *dma_addr))
 		goto error_free_page;
 
+	svmm = spage->zone_device_data;
+	mutex_lock(&svmm->mutex);
+	nouveau_svmm_invalidate(svmm, args->start, args->end);
 	if (drm->dmem->migrate.copy_func(drm, 1, NOUVEAU_APER_HOST, *dma_addr,
 			NOUVEAU_APER_VRAM, nouveau_dmem_page_addr(spage)))
 		goto error_dma_unmap;
+	mutex_unlock(&svmm->mutex);
 
 	args->dst[0] = migrate_pfn(page_to_pfn(dpage)) | MIGRATE_PFN_LOCKED;
 	return 0;
 
 error_dma_unmap:
+	mutex_unlock(&svmm->mutex);
 	dma_unmap_page(dev, *dma_addr, PAGE_SIZE, DMA_BIDIRECTIONAL);
 error_free_page:
 	__free_page(dpage);
@@ -531,7 +537,8 @@ nouveau_dmem_init(struct nouveau_drm *drm)
 }
 
 static unsigned long nouveau_dmem_migrate_copy_one(struct nouveau_drm *drm,
-		unsigned long src, dma_addr_t *dma_addr, u64 *pfn)
+		struct nouveau_svmm *svmm, unsigned long src,
+		dma_addr_t *dma_addr, u64 *pfn)
 {
 	struct device *dev = drm->dev->dev;
 	struct page *dpage, *spage;
@@ -561,6 +568,7 @@ static unsigned long nouveau_dmem_migrate_copy_one(struct
nouveau_drm *drm,
 			goto out_free_page;
 	}
 
+	dpage->zone_device_data = svmm;
 	*pfn = NVIF_VMM_PFNMAP_V0_V | NVIF_VMM_PFNMAP_V0_VRAM |
 		((paddr >> PAGE_SHIFT) << NVIF_VMM_PFNMAP_V0_ADDR_SHIFT);
 	if (src & MIGRATE_PFN_WRITE)
@@ -584,8 +592,8 @@ static void nouveau_dmem_migrate_chunk(struct nouveau_drm
*drm,
 	unsigned long addr = args->start, nr_dma = 0, i;
 
 	for (i = 0; addr < args->end; i++) {
-		args->dst[i] = nouveau_dmem_migrate_copy_one(drm, args->src[i],
-				dma_addrs + nr_dma, pfns + i);
+		args->dst[i] = nouveau_dmem_migrate_copy_one(drm, svmm,
+				args->src[i], dma_addrs + nr_dma, pfns + i);
 		if (!dma_mapping_error(drm->dev->dev, dma_addrs[nr_dma]))
 			nr_dma++;
 		addr += PAGE_SIZE;
@@ -616,6 +624,7 @@ nouveau_dmem_migrate_vma(struct nouveau_drm *drm,
 	struct migrate_vma args = {
 		.vma		= vma,
 		.start		= start,
+		.pgmap_owner	= drm->dev,
 		.flags		= MIGRATE_VMA_SELECT_SYSTEM,
 	};
 	unsigned long i;
diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c
b/drivers/gpu/drm/nouveau/nouveau_svm.c
index c5f8ca6fb2e3..67b068ac57b2 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -93,17 +93,6 @@ nouveau_ivmm_find(struct nouveau_svm *svm, u64 inst)
 	return NULL;
 }
 
-struct nouveau_svmm {
-	struct mmu_notifier notifier;
-	struct nouveau_vmm *vmm;
-	struct {
-		unsigned long start;
-		unsigned long limit;
-	} unmanaged;
-
-	struct mutex mutex;
-};
-
 #define SVMM_DBG(s,f,a...)                                                    
\
 	NV_DEBUG((s)->vmm->cli->drm, "svm-%p: "f"\n",
(s), ##a)
 #define SVMM_ERR(s,f,a...)                                                    
\
@@ -246,7 +235,7 @@ nouveau_svmm_join(struct nouveau_svmm *svmm, u64 inst)
 }
 
 /* Invalidate SVMM address-range on GPU. */
-static void
+void
 nouveau_svmm_invalidate(struct nouveau_svmm *svmm, u64 start, u64 limit)
 {
 	if (limit > start) {
@@ -279,6 +268,14 @@ nouveau_svmm_invalidate_range_start(struct mmu_notifier
*mn,
 	if (unlikely(!svmm->vmm))
 		goto out;
 
+	/*
+	 * Ignore invalidation callbacks for device private pages since
+	 * the invalidation is handled as part of the migration process.
+	 */
+	if (update->event == MMU_NOTIFY_MIGRATE &&
+	    update->migrate_pgmap_owner == svmm->vmm->cli->drm->dev)
+		goto out;
+
 	if (limit > svmm->unmanaged.start && start <
svmm->unmanaged.limit) {
 		if (start < svmm->unmanaged.start) {
 			nouveau_svmm_invalidate(svmm, start,
diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.h
b/drivers/gpu/drm/nouveau/nouveau_svm.h
index f0fcd1b72e8b..e7d63d7f0c2d 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.h
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.h
@@ -1,11 +1,21 @@
 #ifndef __NOUVEAU_SVM_H__
 #define __NOUVEAU_SVM_H__
 #include <nvif/os.h>
+#include <linux/mmu_notifier.h>
 struct drm_device;
 struct drm_file;
 struct nouveau_drm;
 
-struct nouveau_svmm;
+struct nouveau_svmm {
+	struct mmu_notifier notifier;
+	struct nouveau_vmm *vmm;
+	struct {
+		unsigned long start;
+		unsigned long limit;
+	} unmanaged;
+
+	struct mutex mutex;
+};
 
 #if IS_ENABLED(CONFIG_DRM_NOUVEAU_SVM)
 void nouveau_svm_init(struct nouveau_drm *);
@@ -19,6 +29,7 @@ int nouveau_svmm_join(struct nouveau_svmm *, u64 inst);
 void nouveau_svmm_part(struct nouveau_svmm *, u64 inst);
 int nouveau_svmm_bind(struct drm_device *, void *, struct drm_file *);
 
+void nouveau_svmm_invalidate(struct nouveau_svmm *svmm, u64 start, u64 limit);
 u64 *nouveau_pfns_alloc(unsigned long npages);
 void nouveau_pfns_free(u64 *pfns);
 void nouveau_pfns_map(struct nouveau_svmm *svmm, struct mm_struct *mm,
-- 
2.20.1

Use the new MMU_NOTIFY_MIGRATE event to skip MMU invalidations of device
private memory and handle the invalidation in the driver as part of
migrating device private memory.

Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
---
 lib/test_hmm.c                         | 30 +++++++++++++++-----------
 tools/testing/selftests/vm/hmm-tests.c | 18 ++++++++++++----
 2 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 74c6ee66ef15..9abc9ad3140f 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -214,6 +214,14 @@ static bool dmirror_interval_invalidate(struct
mmu_interval_notifier *mni,
 {
 	struct dmirror *dmirror = container_of(mni, struct dmirror, notifier);
 
+	/*
+	 * Ignore invalidation callbacks for device private pages since
+	 * the invalidation is handled as part of the migration process.
+	 */
+	if (range->event == MMU_NOTIFY_MIGRATE &&
+	    range->migrate_pgmap_owner == dmirror->mdevice)
+		return true;
+
 	if (mmu_notifier_range_blockable(range))
 		mutex_lock(&dmirror->mutex);
 	else if (!mutex_trylock(&dmirror->mutex))
@@ -702,7 +710,7 @@ static int dmirror_migrate(struct dmirror *dmirror,
 		args.dst = dst_pfns;
 		args.start = addr;
 		args.end = next;
-		args.pgmap_owner = NULL;
+		args.pgmap_owner = dmirror->mdevice;
 		args.flags = MIGRATE_VMA_SELECT_SYSTEM;
 		ret = migrate_vma_setup(&args);
 		if (ret)
@@ -992,7 +1000,7 @@ static void dmirror_devmem_free(struct page *page)
 }
 
 static vm_fault_t dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
-						struct dmirror_device *mdevice)
+						      struct dmirror *dmirror)
 {
 	const unsigned long *src = args->src;
 	unsigned long *dst = args->dst;
@@ -1014,6 +1022,7 @@ static vm_fault_t
dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
 			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)
@@ -1022,15 +1031,6 @@ static vm_fault_t
dmirror_devmem_fault_alloc_and_copy(struct migrate_vma *args,
 	return 0;
 }
 
-static void dmirror_devmem_fault_finalize_and_map(struct migrate_vma *args,
-						  struct dmirror *dmirror)
-{
-	/* Invalidate the device's page table mapping. */
-	mutex_lock(&dmirror->mutex);
-	dmirror_do_update(dmirror, args->start, args->end);
-	mutex_unlock(&dmirror->mutex);
-}
-
 static vm_fault_t dmirror_devmem_fault(struct vm_fault *vmf)
 {
 	struct migrate_vma args;
@@ -1060,11 +1060,15 @@ static vm_fault_t dmirror_devmem_fault(struct vm_fault
*vmf)
 	if (migrate_vma_setup(&args))
 		return VM_FAULT_SIGBUS;
 
-	ret = dmirror_devmem_fault_alloc_and_copy(&args, dmirror->mdevice);
+	ret = dmirror_devmem_fault_alloc_and_copy(&args, dmirror);
 	if (ret)
 		return ret;
 	migrate_vma_pages(&args);
-	dmirror_devmem_fault_finalize_and_map(&args, dmirror);
+	/*
+	 * No device finalize step is needed since
+	 * dmirror_devmem_fault_alloc_and_copy() will have already
+	 * invalidated the device page table.
+	 */
 	migrate_vma_finalize(&args);
 	return 0;
 }
diff --git a/tools/testing/selftests/vm/hmm-tests.c
b/tools/testing/selftests/vm/hmm-tests.c
index b533dd08da1d..91d38a29956b 100644
--- a/tools/testing/selftests/vm/hmm-tests.c
+++ b/tools/testing/selftests/vm/hmm-tests.c
@@ -881,8 +881,9 @@ TEST_F(hmm, migrate)
 }
 
 /*
- * Migrate anonymous memory to device private memory and fault it back to
system
- * memory.
+ * Migrate anonymous memory to device private memory and fault some of it back
+ * to system memory, then try migrating the resulting mix of system and device
+ * private memory to the device.
  */
 TEST_F(hmm, migrate_fault)
 {
@@ -924,8 +925,17 @@ TEST_F(hmm, migrate_fault)
 	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. */
-	for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+	/* Fault half the pages back to system memory and check them. */
+	for (i = 0, ptr = buffer->ptr; i < size / (2 * sizeof(*ptr)); ++i)
+		ASSERT_EQ(ptr[i], i);
+
+	/* Migrate memory to the device again. */
+	ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_MIGRATE, buffer, npages);
+	ASSERT_EQ(ret, 0);
+	ASSERT_EQ(buffer->cpages, npages);
+
+	/* Check what the device read. */
+	for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
 		ASSERT_EQ(ptr[i], i);
 
 	hmm_buffer_free(buffer);
-- 
2.20.1

On Tue, Jul 21, 2020 at 02:31:16PM -0700, Ralph Campbell
wrote:
> The src_owner field in struct migrate_vma is being used for two purposes,
> it acts as a selection filter for which types of pages are to be migrated
> and it identifies device private pages owned by the caller. Split this
> into separate parameters so the src_owner field can be used just to
> identify device private pages owned by the caller of migrate_vma_setup().
> Rename the src_owner field to pgmap_owner to reflect it is now used only
> to identify which device private pages to migrate.
> 
> Signed-off-by: Ralph Campbell <rcampbell at nvidia.com>
> ---
>  arch/powerpc/kvm/book3s_hv_uvmem.c     |  4 +++-
>  drivers/gpu/drm/nouveau/nouveau_dmem.c |  4 +++-
>  include/linux/migrate.h                | 13 +++++++++----
>  lib/test_hmm.c                         |  6 ++++--
>  mm/migrate.c                           |  6 ++++--
>  5 files changed, 23 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c
b/arch/powerpc/kvm/book3s_hv_uvmem.c
> index 09d8119024db..6850bd04bcb9 100644
> --- a/arch/powerpc/kvm/book3s_hv_uvmem.c
> +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
> @@ -400,6 +400,7 @@ kvmppc_svm_page_in(struct vm_area_struct *vma, unsigned
long start,
>  	mig.end = end;
>  	mig.src = &src_pfn;
>  	mig.dst = &dst_pfn;
> +	mig.flags = MIGRATE_VMA_SELECT_SYSTEM;
>  
>  	/*
>  	 * We come here with mmap_lock write lock held just for
> @@ -577,7 +578,8 @@ kvmppc_svm_page_out(struct vm_area_struct *vma,
unsigned long start,
>  	mig.end = end;
>  	mig.src = &src_pfn;
>  	mig.dst = &dst_pfn;
> -	mig.src_owner = &kvmppc_uvmem_pgmap;
> +	mig.pgmap_owner = &kvmppc_uvmem_pgmap;
> +	mig.flags = MIGRATE_VMA_SELECT_DEVICE_PRIVATE;
>  
>  	mutex_lock(&kvm->arch.uvmem_lock);
For the kvmppc changes above,
Reviewed-by: Bharata B Rao <bharata at linux.ibm.com>