This is a note to let you know that I've just added the patch titled
powerpc/64s/radix: Fix soft dirty tracking
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-64s-radix-fix-soft-dirty-tracking.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit eea2d6aa84aed635e7dfd151fd07f33d4b7956c6
Author: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Date: Thu May 11 21:42:24 2023 +1000
powerpc/64s/radix: Fix soft dirty tracking
[ Upstream commit 66b2ca086210732954a7790d63d35542936fc664 ]
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@xxxxxxxxxxxxxxx # v4.7+
Reported-by: Dan Horák <dan@xxxxxxxx>
Link: https://lore.kernel.org/r/20230511095558.56663a50f86bdc4cd97700b7@xxxxxxxx
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://msgid.link/20230511114224.977423-1-mpe@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index 9ee235fca4278..75cbedaac5d26 100644
--- a/arch/powerpc/mm/pgtable-radix.c
+++ b/arch/powerpc/mm/pgtable-radix.c
@@ -1041,8 +1041,8 @@ 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);
/*
