From: David Matlack Date: Fri, 1 Apr 2022 17:55:32 +0000 Subject: [PATCH v3 01/23] KVM: x86/mmu: Optimize MMU page cache lookup for all direct SPs In-Reply-To: <20220401175554.1931568-1-dmatlack@google.com> References: <20220401175554.1931568-1-dmatlack@google.com> Message-ID: <20220401175554.1931568-2-dmatlack@google.com> List-Id: To: kvm-riscv@lists.infradead.org MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Commit fb58a9c345f6 ("KVM: x86/mmu: Optimize MMU page cache lookup for fully direct MMUs") skipped the unsync checks and write flood clearing for full direct MMUs. We can extend this further to skip the checks for all direct shadow pages. Direct shadow pages in indirect MMUs (i.e. shadow paging) are used when shadowing a guest huge page with smaller pages. Such direct shadow pages, like their counterparts in fully direct MMUs, are never marked unsynced or have a non-zero write-flooding count. Checking sp->role.direct also generates better code than checking direct_map because, due to register pressure, direct_map has to get shoved onto the stack and then pulled back off. No functional change intended. Reviewed-by: Sean Christopherson Reviewed-by: Peter Xu Signed-off-by: David Matlack --- arch/x86/kvm/mmu/mmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 1361eb4599b4..dbfda133adbe 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2034,7 +2034,6 @@ 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; @@ -2075,7 +2074,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, continue; } - if (direct_mmu) + /* unsync and write-flooding only apply to indirect SPs. */ + if (sp->role.direct) goto trace_get_page; if (sp->unsync) { -- 2.35.1.1094.g7c7d902a7c-goog