This is our MEMORY_DEVICE_COHERENT patch series rebased and updated
for current 5.18-rc5.
Changes since the last version:
- Fixed problems with migration during long-term pinning in
get_user_pages
- Open coded vm_normal_lru_pages as suggested in previous code review
- Update hmm_gup_test with more get_user_pages calls, include
hmm_cow_in_device in hmm-test.
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.
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.
Coherent device type pages at gup are now migrated back to system
memory if they are being pinned long-term (FOLL_LONGTERM). The reason
is, that long-term pinning would interfere with the device memory
manager owning the device-coherent pages (e.g. evictions in TTM).
These series incorporate Alistair Popple patches to do this
migration from pin_user_pages() calls. hmm_gup_test has been added to
hmm-test to test different get user pages calls.
This series includes handling of device-managed anonymous pages
returned by vm_normal_pages. Although they behave like normal pages
for purposes of mapping in CPU page tables and for COW, they do not
support LRU lists, NUMA migration or THP.
We also introduced a FOLL_LRU flag that adds the same behaviour to
follow_page and related APIs, to allow callers to specify that they
expect to put pages on an LRU list.
Alex Sierra (13):
mm: add zone device coherent type memory support
mm: add device coherent vma selection for memory migration
mm: add device coherent checker to remove migration pte
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
mm: handling Non-LRU pages returned by vm_normal_pages
tools: add hmm gup tests for device coherent type
tools: add selftests to hmm for COW in device memory
Alistair Popple (2):
mm: remove the vma check in migrate_vma_setup()
mm/gup: migrate device coherent pages when pinning instead of failing
drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 33 ++-
fs/proc/task_mmu.c | 2 +-
include/linux/memremap.h | 19 ++
include/linux/migrate.h | 1 +
include/linux/mm.h | 3 +-
lib/test_hmm.c | 349 +++++++++++++++++------
lib/test_hmm_uapi.h | 22 +-
mm/gup.c | 49 +++-
mm/huge_memory.c | 2 +-
mm/internal.h | 1 +
mm/khugepaged.c | 9 +-
mm/ksm.c | 6 +-
mm/madvise.c | 4 +-
mm/memcontrol.c | 7 +-
mm/memory-failure.c | 8 +-
mm/memory.c | 9 +-
mm/mempolicy.c | 2 +-
mm/memremap.c | 10 +
mm/migrate.c | 7 +-
mm/migrate_device.c | 115 ++++++--
mm/mlock.c | 2 +-
mm/mprotect.c | 2 +-
mm/rmap.c | 3 +-
tools/testing/selftests/vm/hmm-tests.c | 307 ++++++++++++++++++--
tools/testing/selftests/vm/test_hmm.sh | 24 +-
25 files changed, 814 insertions(+), 182 deletions(-)
--
2.32.0
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]>
Acked-by: Felix Kuehling <[email protected]>
Reviewed-by: Alistair Popple <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
---
tools/testing/selftests/vm/hmm-tests.c | 123 ++++++++++++++++++++-----
1 file changed, 102 insertions(+), 21 deletions(-)
diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
index 203323967b50..84ec8c4a1dc7 100644
--- a/tools/testing/selftests/vm/hmm-tests.c
+++ b/tools/testing/selftests/vm/hmm-tests.c
@@ -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);
@@ -1116,7 +1184,13 @@ 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);
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(buffer->cpages, npages);
+ }
+
for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
ASSERT_EQ(ptr[i], i);
@@ -1354,13 +1428,13 @@ 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);
@@ -1377,9 +1451,16 @@ 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);
}
--
2.32.0
The objective is to test device migration mechanism in pages marked
as COW, for private and coherent device type. In case of writing to
COW private page(s), a page fault will migrate pages back to system
memory first. Then, these pages will be duplicated. In case of COW
device coherent type, pages are duplicated directly from device
memory.
Signed-off-by: Alex Sierra <[email protected]>
Acked-by: Felix Kuehling <[email protected]>
---
tools/testing/selftests/vm/hmm-tests.c | 80 ++++++++++++++++++++++++++
1 file changed, 80 insertions(+)
diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
index 65e30ab6494c..d70b780df877 100644
--- a/tools/testing/selftests/vm/hmm-tests.c
+++ b/tools/testing/selftests/vm/hmm-tests.c
@@ -1870,4 +1870,84 @@ TEST_F(hmm, hmm_gup_test)
close(gup_fd);
hmm_buffer_free(buffer);
}
+
+/*
+ * Test copy-on-write in device pages.
+ * In case of writing to COW private page(s), a page fault will migrate pages
+ * back to system memory first. Then, these pages will be duplicated. In case
+ * of COW device coherent type, pages are duplicated directly from device
+ * memory.
+ */
+TEST_F(hmm, hmm_cow_in_device)
+{
+ struct hmm_buffer *buffer;
+ unsigned long npages;
+ unsigned long size;
+ unsigned long i;
+ int *ptr;
+ int ret;
+ unsigned char *m;
+ pid_t pid;
+ int status;
+
+ npages = 4;
+ size = npages << self->page_shift;
+
+ buffer = malloc(sizeof(*buffer));
+ ASSERT_NE(buffer, NULL);
+
+ buffer->fd = -1;
+ buffer->size = size;
+ buffer->mirror = malloc(size);
+ ASSERT_NE(buffer->mirror, NULL);
+
+ buffer->ptr = mmap(NULL, size,
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS,
+ buffer->fd, 0);
+ ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+ /* Initialize buffer in system memory. */
+ for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+ ptr[i] = i;
+
+ /* Migrate memory to device. */
+
+ ret = hmm_migrate_sys_to_dev(self->fd, buffer, npages);
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(buffer->cpages, npages);
+
+ pid = fork();
+ if (pid == -1)
+ ASSERT_EQ(pid, 0);
+ if (!pid) {
+ /* Child process waitd for SIGTERM from the parent. */
+ while (1) {
+ }
+ perror("Should not reach this\n");
+ exit(0);
+ }
+ /* Parent process writes to COW pages(s) and gets a
+ * new copy in system. In case of device private pages,
+ * this write causes a migration to system mem first.
+ */
+ for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
+ ptr[i] = i;
+
+ /* Terminate child and wait */
+ EXPECT_EQ(0, kill(pid, SIGTERM));
+ EXPECT_EQ(pid, waitpid(pid, &status, 0));
+ EXPECT_NE(0, WIFSIGNALED(status));
+ EXPECT_EQ(SIGTERM, WTERMSIG(status));
+
+ /* Take snapshot to CPU pagetables */
+ ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages);
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(buffer->cpages, npages);
+ m = buffer->mirror;
+ for (i = 0; i < npages; i++)
+ ASSERT_EQ(HMM_DMIRROR_PROT_WRITE, m[i]);
+
+ hmm_buffer_free(buffer);
+}
TEST_HARNESS_MAIN
--
2.32.0
During remove_migration_pte(), entries for device coherent type pages
that were not created through special migration ptes, ignore _PAGE_RW
flag. This path can be found at migrate_device_page(), where valid
vma is not required. In this case, migrate_vma_collect_pmd() is not
called and special migration ptes are not set.
Signed-off-by: Alex Sierra <[email protected]>
---
mm/migrate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/migrate.c b/mm/migrate.c
index 6c31ee1e1c9b..e18ddee56f37 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -206,7 +206,8 @@ static bool remove_migration_pte(struct folio *folio,
* Recheck VMA as permissions can change since migration started
*/
entry = pte_to_swp_entry(*pvmw.pte);
- if (is_writable_migration_entry(entry))
+ if (is_writable_migration_entry(entry) ||
+ is_device_coherent_page(pfn_to_page(pvmw.pfn)))
pte = maybe_mkwrite(pte, vma);
else if (pte_swp_uffd_wp(*pvmw.pte))
pte = pte_mkuffd_wp(pte);
--
2.32.0
From: Alistair Popple <[email protected]>
Currently any attempts to pin a device coherent page will fail. This is
because device coherent pages need to be managed by a device driver, and
pinning them would prevent a driver from migrating them off the device.
However this is no reason to fail pinning of these pages. These are
coherent and accessible from the CPU so can be migrated just like
pinning ZONE_MOVABLE pages. So instead of failing all attempts to pin
them first try migrating them out of ZONE_DEVICE.
Signed-off-by: Alistair Popple <[email protected]>
Acked-by: Felix Kuehling <[email protected]>
[hch: rebased to the split device memory checks,
moved migrate_device_page to migrate_device.c]
Signed-off-by: Christoph Hellwig <[email protected]>
---
mm/gup.c | 47 +++++++++++++++++++++++++++++++++++-----
mm/internal.h | 1 +
mm/migrate_device.c | 53 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 96 insertions(+), 5 deletions(-)
diff --git a/mm/gup.c b/mm/gup.c
index f598a037eb04..a214c8df7140 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1786,9 +1786,43 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
continue;
prev_folio = folio;
- if (folio_is_pinnable(folio))
+ /*
+ * Device private pages will get faulted in during gup so it
+ * shouldn't be possible to see one here.
+ */
+ if (WARN_ON_ONCE(folio_is_device_private(folio))) {
+ ret = -EFAULT;
+ goto unpin_pages;
+ }
+
+ /*
+ * Device coherent pages are managed by a driver and should not
+ * be pinned indefinitely as it prevents the driver moving the
+ * page. So when trying to pin with FOLL_LONGTERM instead try
+ * to migrate the page out of device memory.
+ */
+ if (folio_is_device_coherent(folio)) {
+ WARN_ON_ONCE(PageCompound(&folio->page));
+
+ /*
+ * Migration will fail if the page is pinned, so convert
+ * the pin on the source page to a normal reference.
+ */
+ if (gup_flags & FOLL_PIN) {
+ get_page(&folio->page);
+ unpin_user_page(&folio->page);
+ }
+
+ pages[i] = migrate_device_page(&folio->page, gup_flags);
+ if (!pages[i]) {
+ ret = -EBUSY;
+ goto unpin_pages;
+ }
continue;
+ }
+ if (folio_is_pinnable(folio))
+ continue;
/*
* Try to move out any movable page before pinning the range.
*/
@@ -1824,10 +1858,13 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
return nr_pages;
unpin_pages:
- if (gup_flags & FOLL_PIN) {
- unpin_user_pages(pages, nr_pages);
- } else {
- for (i = 0; i < nr_pages; i++)
+ for (i = 0; i < nr_pages; i++) {
+ if (!pages[i])
+ continue;
+
+ if (gup_flags & FOLL_PIN)
+ unpin_user_page(pages[i]);
+ else
put_page(pages[i]);
}
diff --git a/mm/internal.h b/mm/internal.h
index cf16280ce132..32c621416966 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -750,6 +750,7 @@ int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
unsigned long addr, int page_nid, int *flags);
void free_zone_device_page(struct page *page);
+struct page *migrate_device_page(struct page *page, unsigned int gup_flags);
/*
* mm/gup.c
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index b399c498f0aa..1e74aa7ab580 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -775,3 +775,56 @@ void migrate_vma_finalize(struct migrate_vma *migrate)
}
}
EXPORT_SYMBOL(migrate_vma_finalize);
+
+/*
+ * Migrate a device coherent page back to normal memory. The caller should have
+ * a reference on page which will be copied to the new page if migration is
+ * successful or dropped on failure.
+ */
+struct page *migrate_device_page(struct page *page, unsigned int gup_flags)
+{
+ unsigned long src_pfn, dst_pfn = 0;
+ struct migrate_vma args;
+ struct page *dpage;
+
+ lock_page(page);
+ src_pfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE;
+ args.src = &src_pfn;
+ args.dst = &dst_pfn;
+ args.cpages = 1;
+ args.npages = 1;
+ args.vma = NULL;
+ migrate_vma_setup(&args);
+ if (!(src_pfn & MIGRATE_PFN_MIGRATE))
+ return NULL;
+
+ dpage = alloc_pages(GFP_USER | __GFP_NOWARN, 0);
+
+ /*
+ * get/pin the new page now so we don't have to retry gup after
+ * migrating. We already have a reference so this should never fail.
+ */
+ if (dpage && WARN_ON_ONCE(!try_grab_page(dpage, gup_flags))) {
+ __free_pages(dpage, 0);
+ dpage = NULL;
+ }
+
+ if (dpage) {
+ lock_page(dpage);
+ dst_pfn = migrate_pfn(page_to_pfn(dpage));
+ }
+
+ migrate_vma_pages(&args);
+ if (src_pfn & MIGRATE_PFN_MIGRATE)
+ copy_highpage(dpage, page);
+ migrate_vma_finalize(&args);
+ if (dpage && !(src_pfn & MIGRATE_PFN_MIGRATE)) {
+ if (gup_flags & FOLL_PIN)
+ unpin_user_page(dpage);
+ else
+ put_page(dpage);
+ dpage = NULL;
+ }
+
+ return dpage;
+}
--
2.32.0