[PATCH v13 70/85] KVM: MIPS: Mark "struct page" pfns accessed only in "slow" page fault path
From: Sean Christopherson <seanjc@google.com>
Date: 2024-10-10 18:27:21
Also in:
kvm, kvm-riscv, kvmarm, linux-arm-kernel, linux-mips, linux-riscv, lkml, loongarch
Subsystem:
kernel virtual machine for mips (kvm/mips), mips, the rest · Maintainers:
Huacai Chen, Thomas Bogendoerfer, Linus Torvalds
Mark pages accessed only in the slow page fault path in order to remove an unnecessary user of kvm_pfn_to_refcounted_page(). Marking pages accessed in the primary MMU during KVM page fault handling isn't harmful, but it's largely pointless and likely a waste of a cycles since the primary MMU will call into KVM via mmu_notifiers when aging pages. I.e. KVM participates in a "pull" model, so there's no need to also "push" updates. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/mips/kvm/mmu.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-)
diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
index 4da9ce4eb54d..f1e4b618ec6d 100644
--- a/arch/mips/kvm/mmu.c
+++ b/arch/mips/kvm/mmu.c@@ -484,8 +484,6 @@ static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, struct kvm *kvm = vcpu->kvm; gfn_t gfn = gpa >> PAGE_SHIFT; pte_t *ptep; - kvm_pfn_t pfn = 0; /* silence bogus GCC warning */ - bool pfn_valid = false; int ret = 0; spin_lock(&kvm->mmu_lock);
@@ -498,12 +496,9 @@ static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, } /* Track access to pages marked old */ - if (!pte_young(*ptep)) { + if (!pte_young(*ptep)) set_pte(ptep, pte_mkyoung(*ptep)); - pfn = pte_pfn(*ptep); - pfn_valid = true; - /* call kvm_set_pfn_accessed() after unlock */ - } + if (write_fault && !pte_dirty(*ptep)) { if (!pte_write(*ptep)) { ret = -EFAULT;
@@ -512,7 +507,6 @@ static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, /* Track dirtying of writeable pages */ set_pte(ptep, pte_mkdirty(*ptep)); - pfn = pte_pfn(*ptep); mark_page_dirty(kvm, gfn); }
@@ -523,8 +517,6 @@ static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, out: spin_unlock(&kvm->mmu_lock); - if (pfn_valid) - kvm_set_pfn_accessed(pfn); return ret; }
--
2.47.0.rc1.288.g06298d1525-goog