Commit df89b175 authored May 11, 2023 by Michael Ellerman Committed by Greg Kroah-Hartman May 30, 2023

powerpc/64s/radix: Fix soft dirty tracking



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: b0b5e9b1 ("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>

parent 60b9a9c8

arch/powerpc/mm/book3s64/radix_pgtable.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -1018,8 +1018,8 @@ void radix__ptep_set_access_flags(struct vm_area_struct vma, pte_t ptep,
	pte_t entry, unsigned long address, int psize)		pte_t entry, unsigned long address, int psize)
	{		{
	struct mm_struct *mm = vma->vm_mm;		struct mm_struct *mm = vma->vm_mm;
	unsigned long set = pte_val(entry) & (_PAGE_DIRTY \| _PAGE_ACCESSED \|		unsigned long set = pte_val(entry) & (_PAGE_DIRTY \| _PAGE_SOFT_DIRTY \|
	_PAGE_RW \| _PAGE_EXEC);		_PAGE_ACCESSED \| _PAGE_RW \| _PAGE_EXEC);

	unsigned long change = pte_val(entry) ^ pte_val(*ptep);		unsigned long change = pte_val(entry) ^ pte_val(*ptep);
	/*		/*