On 2024/7/27 上午7:52, Sean Christopherson wrote:
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@xxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/loongarch/kvm/mmu.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c
index 2634a9e8d82c..364dd35e0557 100644
--- a/arch/loongarch/kvm/mmu.c
+++ b/arch/loongarch/kvm/mmu.c
@@ -608,13 +608,13 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
if (kvm_pte_young(changed))
kvm_set_pfn_accessed(pfn);
- if (kvm_pte_dirty(changed)) {
- mark_page_dirty(kvm, gfn);
- kvm_set_pfn_dirty(pfn);
- }
if (page)
put_page(page);
}
+
+ if (kvm_pte_dirty(changed))
+ mark_page_dirty(kvm, gfn);
+
return ret;
out:
spin_unlock(&kvm->mmu_lock);
@@ -915,12 +915,14 @@ static int kvm_map_page(struct kvm_vcpu *vcpu, unsigned long gpa, bool write)
else
++kvm->stat.pages;
kvm_set_pte(ptep, new_pte);
- spin_unlock(&kvm->mmu_lock);
- if (prot_bits & _PAGE_DIRTY) {
- mark_page_dirty_in_slot(kvm, memslot, gfn);
+ if (writeable)
Is it better to use write or (prot_bits & _PAGE_DIRTY) here? writable
is pte permission from function hva_to_pfn_slow(), write is fault action.
Regards
Bibo Mao
kvm_set_pfn_dirty(pfn);
- }
+
+ spin_unlock(&kvm->mmu_lock);
+
+ if (prot_bits & _PAGE_DIRTY)
+ mark_page_dirty_in_slot(kvm, memslot, gfn);
kvm_release_pfn_clean(pfn);
out:
