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tools: add selftests to hmm for COW in device memory

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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.

Link: https://lkml.kernel.org/r/20220715150521.18165-15-alex.sierra@amd.com
Signed-off-by: Alex Sierra <alex.sierra@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alex Sierra 2022-07-15 10:05:21 -05:00 committed by akpm
parent 9e09b705fd
commit 96c0657383
1 changed files with 80 additions and 0 deletions
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80
tools/testing/selftests/vm/hmm-tests.c
View file

@ -1874,4 +1874,84 @@ TEST_F(hmm, hmm_gup_test)
close(gup_fd); close(gup_fd);
hmm_buffer_free(buffer); 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 TEST_HARNESS_MAIN