On 5/30/26 18:54, Dev Jain wrote:
> To cover pagemap paths scanning PMD entries, add assertions to check
> whether a device-private PMD entry has the correct pagemap information -
> the PM_SWAP bit must be on in the pagemap entry. Before that, we must
> assert through HMM_DMIRROR_SNAPSHOT snapshot that the leaf entry is
> at PMD level and not PTE level.
>
> Signed-off-by: Dev Jain <[email protected]>
> ---
> tools/testing/selftests/mm/hmm-tests.c | 29 ++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/hmm-tests.c
> b/tools/testing/selftests/mm/hmm-tests.c
> index e1c8a679a4cf3..d09d4a9081de1 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2276,8 +2276,11 @@ TEST_F(hmm, migrate_anon_huge_fault)
> unsigned long npages;
> unsigned long size;
> unsigned long i;
> + unsigned char *m;
> + uint64_t entry;
> void *old_ptr;
> void *map;
> + int pagemap_fd;
> int *ptr;
> int ret;
>
> @@ -2318,6 +2321,32 @@ TEST_F(hmm, migrate_anon_huge_fault)
> for (i = 0, ptr = buffer->mirror; i < size / sizeof(*ptr); ++i)
> ASSERT_EQ(ptr[i], i);
>
> + if (!hmm_is_coherent_type(variant->device_number)) {
> + 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(m[i], HMM_DMIRROR_PROT_DEV_PRIVATE_LOCAL |
> + HMM_DMIRROR_PROT_WRITE |
> + HMM_DMIRROR_PROT_PMD);
madvise(..., MADV_HUGEPAGE) is not sufficient to guarantee that the allocation
was indeed converted to THP. Might be worth using the kpageflags interface (but
that
requires elevated privileges) and then KPF_THP? Otherwise the
HMM_DMIRROR_PROT_PMD
can be a miss from time to time. One other option is not to assert, but to check
and inform?
> +
> + pagemap_fd = open("/proc/self/pagemap", O_RDONLY);
> + ASSERT_GE(pagemap_fd, 0);
> +
> + for (i = 0; i < npages; ++i) {
> + entry = pagemap_get_entry(pagemap_fd,
> + (char *)buffer->ptr + i *
> self->page_size);
> +
If this is a THP entry, do we have valid pagemap entries for offset of i *
page_size?
> + ASSERT_NE(entry & PM_SWAP, 0);
> + ASSERT_EQ(entry & PM_PRESENT, 0);
Nit: You can use PAGEMAP_PRESENT()
> + }
> +
> + close(pagemap_fd);
> + }
> +
> /* Fault pages back to system memory and check them. */
> for (i = 0, ptr = buffer->ptr; i < size / sizeof(*ptr); ++i)
> ASSERT_EQ(ptr[i], i);
Balbir Singh
