[PATCH v13 65/85] KVM: LoongArch: Mark "struct page" pfns dirty only in "slow" page fault path
From: Sean Christopherson <seanjc@google.com>
Date: 2024-10-10 18:27:10
Also in:
kvm, kvm-riscv, kvmarm, linux-arm-kernel, linux-mips, linux-riscv, lkml, loongarch
Subsystem:
kernel virtual machine for loongarch (kvm/loongarch), loongarch, the rest · Maintainers:
Tianrui Zhao, Bibo Mao, Huacai Chen, Linus Torvalds
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 (local) Reviewed-by: Bibo Mao <maobibo@loongson.cn> Signed-off-by: Sean Christopherson <seanjc@google.com> --- 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 28681dfb4b85..cc2a5f289b14 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) 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:
--
2.47.0.rc1.288.g06298d1525-goog