The patch titled
Subject: mm/hmm: fault non-owner device private entries
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-hmm-fault-non-owner-device-private-entries.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hmm-fault-non-owner-device-private-entries.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Ralph Campbell <rcampbell@xxxxxxxxxx>
Subject: mm/hmm: fault non-owner device private entries
Date: Mon, 25 Jul 2022 11:36:14 -0700
If hmm_range_fault() is called with the HMM_PFN_REQ_FAULT flag and a
device private PTE is found, the hmm_range::dev_private_owner page is used
to determine if the device private page should not be faulted in.
However, if the device private page is not owned by the caller,
hmm_range_fault() returns an error instead of calling migrate_to_ram() to
fault in the page.
Link: https://lkml.kernel.org/r/20220725183615.4118795-2-rcampbell@xxxxxxxxxx
Fixes: 76612d6ce4cc ("mm/hmm: reorganize how !pte_present is handled in hmm_vma_handle_pte()")
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Reported-by: Felix Kuehling <felix.kuehling@xxxxxxx>
Cc: Philip Yang <Philip.Yang@xxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hmm.c | 19 ++++++++-----------
1 file changed, 8 insertions(+), 11 deletions(-)
--- a/mm/hmm.c~mm-hmm-fault-non-owner-device-private-entries
+++ a/mm/hmm.c
@@ -212,14 +212,6 @@ int hmm_vma_handle_pmd(struct mm_walk *w
unsigned long end, unsigned long hmm_pfns[], pmd_t pmd);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-static inline bool hmm_is_device_private_entry(struct hmm_range *range,
- swp_entry_t entry)
-{
- return is_device_private_entry(entry) &&
- pfn_swap_entry_to_page(entry)->pgmap->owner ==
- range->dev_private_owner;
-}
-
static inline unsigned long pte_to_hmm_pfn_flags(struct hmm_range *range,
pte_t pte)
{
@@ -252,10 +244,12 @@ static int hmm_vma_handle_pte(struct mm_
swp_entry_t entry = pte_to_swp_entry(pte);
/*
- * Never fault in device private pages, but just report
- * the PFN even if not present.
+ * Don't fault in device private pages owned by the caller,
+ * just report the PFN.
*/
- if (hmm_is_device_private_entry(range, entry)) {
+ if (is_device_private_entry(entry) &&
+ pfn_swap_entry_to_page(entry)->pgmap->owner ==
+ range->dev_private_owner) {
cpu_flags = HMM_PFN_VALID;
if (is_writable_device_private_entry(entry))
cpu_flags |= HMM_PFN_WRITE;
@@ -273,6 +267,9 @@ static int hmm_vma_handle_pte(struct mm_
if (!non_swap_entry(entry))
goto fault;
+ if (is_device_private_entry(entry))
+ goto fault;
+
if (is_device_exclusive_entry(entry))
goto fault;
_
Patches currently in -mm which might be from rcampbell@xxxxxxxxxx are
mm-hmm-fault-non-owner-device-private-entries.patch
mm-hmm-add-a-test-for-cross-device-private-faults.patch
