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KVM: MMU: optimize pte write path if don't have protected sp 

Simply return from kvm_mmu_pte_write path if no shadow page is
write-protected, then we can avoid to walk all shadow pages and hold
mmu-lock

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Xiao Guangrong 2011-05-15 23:20:27 +08:00 committed by Avi Kivity
parent 96304217a7
commit 332b207d65
2 changed files with 10 additions and 0 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -441,6 +441,7 @@ struct kvm_arch {
unsigned int n_used_mmu_pages;
unsigned int n_requested_mmu_pages;
unsigned int n_max_mmu_pages;
unsigned int indirect_shadow_pages;
atomic_t invlpg_counter;
struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
/*

9
arch/x86/kvm/mmu.c
View File

@ -498,6 +498,7 @@ static void account_shadowed(struct kvm *kvm, gfn_t gfn)
linfo = lpage_info_slot(gfn, slot, i);
linfo->write_count += 1;
}
kvm->arch.indirect_shadow_pages++;
}
static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
@ -513,6 +514,7 @@ static void unaccount_shadowed(struct kvm *kvm, gfn_t gfn)
linfo->write_count -= 1;
WARN_ON(linfo->write_count < 0);
}
kvm->arch.indirect_shadow_pages--;
}
static int has_wrprotected_page(struct kvm *kvm,
@ -3233,6 +3235,13 @@ void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
int level, npte, invlpg_counter, r, flooded = 0;
bool remote_flush, local_flush, zap_page;
/*
* If we don't have indirect shadow pages, it means no page is
* write-protected, so we can exit simply.
*/
if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
return;
zap_page = remote_flush = local_flush = false;
offset = offset_in_page(gpa);