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KVM: MIPS: Mark "struct page" pfns accessed only in "slow" page fault path

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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>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-71-seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-10-10 11:24:12 -07:00 committed by Paolo Bonzini
parent d8f4cda748
commit 4d75f14fc8
1 changed files with 2 additions and 10 deletions
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12
arch/mips/kvm/mmu.c
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@ -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;
}