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mm/hmm.c: allow VM_MIXEDMAP to work with hmm_range_fault

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commit 87c01d57fa upstream.

hmm_range_fault() can be used instead of get_user_pages() for devices
which allow faulting however unlike get_user_pages() it will return an
error when used on a VM_MIXEDMAP range.

To make hmm_range_fault() more closely match get_user_pages() remove
this restriction.  This requires dealing with the !ARCH_HAS_PTE_SPECIAL
case in hmm_vma_handle_pte().  Rather than replicating the logic of
vm_normal_page() call it directly and do a check for the zero pfn
similar to what get_user_pages() currently does.

Also add a test to hmm selftest to verify functionality.

Link: https://lkml.kernel.org/r/20211104012001.2555676-1-apopple@nvidia.com
Fixes: da4c3c735e ("mm/hmm/mirror: helper to snapshot CPU page table")
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alistair Popple
2022-01-14 14:09:31 -08:00
committed by Greg Kroah-Hartman
parent 33bb7f027b
commit 6292503700
3 changed files with 69 additions and 2 deletions
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42
tools/testing/selftests/vm/hmm-tests.c
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@@ -1242,6 +1242,48 @@ TEST_F(hmm, anon_teardown)
}
}
/*
* Test memory snapshot without faulting in pages accessed by the device.
*/
TEST_F(hmm, mixedmap)
{
struct hmm_buffer *buffer;
unsigned long npages;
unsigned long size;
unsigned char *m;
int ret;
npages = 1;
size = npages << self->page_shift;
buffer = malloc(sizeof(*buffer));
ASSERT_NE(buffer, NULL);
buffer->fd = -1;
buffer->size = size;
buffer->mirror = malloc(npages);
ASSERT_NE(buffer->mirror, NULL);
/* Reserve a range of addresses. */
buffer->ptr = mmap(NULL, size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE,
self->fd, 0);
ASSERT_NE(buffer->ptr, MAP_FAILED);
/* Simulate a device snapshotting CPU pagetables. */
ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages);
ASSERT_EQ(ret, 0);
ASSERT_EQ(buffer->cpages, npages);
/* Check what the device saw. */
m = buffer->mirror;
ASSERT_EQ(m[0], HMM_DMIRROR_PROT_READ);
hmm_buffer_free(buffer);
}
/*
* Test memory snapshot without faulting in pages accessed by the device.
*/