Re: [PATCH v3 2/3] mm/hmm: allow snapshot of the special zero page

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 23.10.19 21:55, Ralph Campbell wrote:
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.

Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
---
  mm/hmm.c | 10 ++++++++--
  1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index acf7a664b38c..8c96c9ddcae5 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -529,8 +529,14 @@ 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;


Acked-by: David Hildenbrand <david@xxxxxxxxxx>

--

Thanks,

David / dhildenb






[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux