From: Michael Ellerman mpe@ellerman.id.au
commit 66b2ca086210732954a7790d63d35542936fc664 upstream.
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 Link: https://msgid.link/20230511114224.977423-1-mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/mm/book3s64/radix_pgtable.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- 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 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); /*