From d8f4cda748eaf1edc2c31275c854277a2aaaa4cf Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 10 Oct 2024 11:24:11 -0700 Subject: [PATCH] KVM: MIPS: Mark "struct page" pfns dirty only in "slow" page fault path Mark pages/folios dirty only the slow page fault path, i.e. only when mmu_lock is held and the operation is mmu_notifier-protected, as marking a page/folio dirty after it has been written back can make some filesystems unhappy (backing KVM guests will such filesystem files is uncommon, and the race is minuscule, hence the lack of complaints). See the link below for details. Link: https://lore.kernel.org/all/cover.1683044162.git.lstoakes@gmail.com Signed-off-by: Sean Christopherson Tested-by: Dmitry Osipenko Signed-off-by: Paolo Bonzini Message-ID: <20241010182427.1434605-70-seanjc@google.com> --- arch/mips/kvm/mmu.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c index c17157e700c03..4da9ce4eb54db 100644 --- a/arch/mips/kvm/mmu.c +++ b/arch/mips/kvm/mmu.c @@ -514,7 +514,6 @@ static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, set_pte(ptep, pte_mkdirty(*ptep)); pfn = pte_pfn(*ptep); mark_page_dirty(kvm, gfn); - kvm_set_pfn_dirty(pfn); } if (out_entry) @@ -628,7 +627,6 @@ retry: if (write_fault) { prot_bits |= __WRITEABLE; mark_page_dirty(kvm, gfn); - kvm_set_pfn_dirty(pfn); } } entry = pfn_pte(pfn, __pgprot(prot_bits)); @@ -642,6 +640,9 @@ retry: if (out_buddy) *out_buddy = *ptep_buddy(ptep); + if (writeable) + kvm_set_pfn_dirty(pfn); + spin_unlock(&kvm->mmu_lock); kvm_release_pfn_clean(pfn); kvm_set_pfn_accessed(pfn); -- 2.47.3