From fb58a9c345f645f1774dcf6a36fda169253008ae Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 23 Jun 2020 12:40:27 -0700 Subject: [PATCH] KVM: x86/mmu: Optimize MMU page cache lookup for fully direct MMUs Skip the unsync checks and the write flooding clearing for fully direct MMUs, which are guaranteed to not have unsync'd or indirect pages (write flooding detection only applies to indirect pages). For TDP, this avoids unnecessary memory reads and writes, and for the write flooding count will also avoid dirtying a cache line (unsync_child_bitmap itself consumes a cache line, i.e. write_flooding_count is guaranteed to be in a different cache line than parent_ptes). Signed-off-by: Sean Christopherson Message-Id: <20200623194027.23135-3-sean.j.christopherson@intel.com> Reviewed-By: Jon Cargille Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 713371316848..1b2988a9f0c6 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2460,6 +2460,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, int direct, unsigned int access) { + bool direct_mmu = vcpu->arch.mmu->direct_map; union kvm_mmu_page_role role; struct hlist_head *sp_list; unsigned quadrant; @@ -2475,8 +2476,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, if (role.direct) role.gpte_is_8_bytes = true; role.access = access; - if (!vcpu->arch.mmu->direct_map - && vcpu->arch.mmu->root_level <= PT32_ROOT_LEVEL) { + if (!direct_mmu && vcpu->arch.mmu->root_level <= PT32_ROOT_LEVEL) { quadrant = gaddr >> (PAGE_SHIFT + (PT64_PT_BITS * level)); quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1; role.quadrant = quadrant; @@ -2495,6 +2495,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, if (sp->role.word != role.word) continue; + if (direct_mmu) + goto trace_get_page; + if (sp->unsync) { /* The page is good, but __kvm_sync_page might still end * up zapping it. If so, break in order to rebuild it. @@ -2510,6 +2513,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); __clear_sp_write_flooding_count(sp); + +trace_get_page: trace_kvm_mmu_get_page(sp, false); goto out; }