Commit d8f4cda7 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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: default avatarSean Christopherson <seanjc@google.com>
Tested-by: default avatarDmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-70-seanjc@google.com>
parent 14d02b7f

arch/mips/kvm/mmu.c

+3 −2
Original line number Diff line number Diff line
@@ -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 @@ static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa, 
		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 @@ static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa, 
	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);