From: Michael Ellerman <mpe@ellerman.id.au>
To: <linuxppc-dev@lists.ozlabs.org>
Cc: dan@danny.cz, aneesh.kumar@linux.ibm.com, npiggin@gmail.com
Subject: [PATCH] powerpc/64s/radix: Fix soft dirty tracking
Date: Thu, 11 May 2023 21:42:24 +1000 [thread overview]
Message-ID: <20230511114224.977423-1-mpe@ellerman.id.au> (raw)
It was reported that soft dirty tracking doesn't work when using the
Radix MMU.
The tracking is supposed to work by clearing the soft dirty bit for a
mapping and then write protecting the PTE. If/when the page is written
to, a page fault occurs and the soft dirty bit is added back via
pte_mkdirty(). For example in wp_page_reuse():
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
update_mmu_cache(vma, vmf->address, vmf->pte);
Unfortunately on radix _PAGE_SOFTDIRTY is being dropped by
radix__ptep_set_access_flags(), called from ptep_set_access_flags(),
meaning the soft dirty bit is not set even though the page has been
written to.
Fix it by adding _PAGE_SOFTDIRTY to the set of bits that are able to be
changed in radix__ptep_set_access_flags().
Fixes: b0b5e9b13047 ("powerpc/mm/radix: Add radix pte #defines")
Cc: stable@vger.kernel.org # v4.7+
Reported-by: Dan Horák <dan@danny.cz>
Link: https://lore.kernel.org/r/20230511095558.56663a50f86bdc4cd97700b7@danny.cz
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
arch/powerpc/mm/book3s64/radix_pgtable.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index 26245aaf12b8..2297aa764ecd 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -1040,8 +1040,8 @@ void radix__ptep_set_access_flags(struct vm_area_struct *vma, pte_t *ptep,
pte_t entry, unsigned long address, int psize)
{
struct mm_struct *mm = vma->vm_mm;
- unsigned long set = pte_val(entry) & (_PAGE_DIRTY | _PAGE_ACCESSED |
- _PAGE_RW | _PAGE_EXEC);
+ unsigned long set = pte_val(entry) & (_PAGE_DIRTY | _PAGE_SOFT_DIRTY |
+ _PAGE_ACCESSED | _PAGE_RW | _PAGE_EXEC);
unsigned long change = pte_val(entry) ^ pte_val(*ptep);
/*
--
2.40.1
next reply other threads:[~2023-05-11 11:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 11:42 Michael Ellerman [this message]
2023-05-15 5:54 ` [PATCH] powerpc/64s/radix: Fix soft dirty tracking Aneesh Kumar K.V
2023-05-15 12:43 ` Dan Horák
2023-07-03 5:21 ` Michael Ellerman
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