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authorRalph Campbell <rcampbell@nvidia.com>2019-10-23 12:55:14 -0700
committerJason Gunthorpe <jgg@mellanox.com>2019-10-29 14:26:28 -0300
commitac541f2503722943a9f13e0c92ed07632ba7fd38 (patch)
tree66c9f31f41501650ebfc34378d0bed0addb111cd /mm/hmm.c
parentd6d5df1db6e9d7f8f76d2911707f7d5877251b02 (diff)
mm/hmm: allow snapshot of the special zero page
If a device driver like nouveau tries to use hmm_range_fault() to access the special shared zero page in system memory, hmm_range_fault() will return -EFAULT and kill the process. Allow hmm_range_fault() to return success (0) when the CPU pagetable entry points to the special shared zero page. page_to_pfn() and pfn_to_page() are defined on the zero page so just handle it like any other page. Link: https://lore.kernel.org/r/20191023195515.13168-3-rcampbell@nvidia.com Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> Reviewed-by: "Jérôme Glisse" <jglisse@redhat.com> Acked-by: David Hildenbrand <david@redhat.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Diffstat (limited to 'mm/hmm.c')
-rw-r--r--mm/hmm.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/mm/hmm.c b/mm/hmm.c
index 902f5fa6bf93..6b0136665407 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -532,8 +532,14 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
if (unlikely(!hmm_vma_walk->pgmap))
return -EBUSY;
} else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte)) {
- *pfn = range->values[HMM_PFN_SPECIAL];
- return -EFAULT;
+ if (!is_zero_pfn(pte_pfn(pte))) {
+ *pfn = range->values[HMM_PFN_SPECIAL];
+ return -EFAULT;
+ }
+ /*
+ * Since each architecture defines a struct page for the zero
+ * page, just fall through and treat it like a normal page.
+ */
}
*pfn = hmm_device_entry_from_pfn(range, pte_pfn(pte)) | cpu_flags;