linux-kernel - [PATCH] KVM: nSVM: Additions to optimizing L12 to L2 vmcb.save copies

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Message-Id: <20210317162930.28135-1-cavery@redhat.com>
Date:   Wed, 17 Mar 2021 12:29:30 -0400
From:   Cathy Avery <cavery@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        pbonzini@...hat.com
Cc:     vkuznets@...hat.com, wei.huang2@....com, seanjc@...gle.com
Subject: [PATCH] KVM: nSVM: Additions to optimizing L12 to L2 vmcb.save copies

Extend using the vmcb12 control clean field to determine which
vmcb12.save registers were marked dirty in order to minimize
register copies by including the CR bit.

This patch also fixes the init of last_vmcb12_gpa by using an invalid
physical address instead of 0.

Tested:
kvm-unit-tests
kvm selftests
Fedora L1 L2

Signed-off-by: Cathy Avery <cavery@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 9 ++++++---
 arch/x86/kvm/svm/svm.c    | 2 +-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 8523f60adb92..6f9a40e002bc 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -449,9 +449,12 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
 	}
 
 	kvm_set_rflags(&svm->vcpu, vmcb12->save.rflags | X86_EFLAGS_FIXED);
-	svm_set_efer(&svm->vcpu, vmcb12->save.efer);
-	svm_set_cr0(&svm->vcpu, vmcb12->save.cr0);
-	svm_set_cr4(&svm->vcpu, vmcb12->save.cr4);
+
+	if (unlikely(new_vmcb12 || vmcb_is_dirty(vmcb12, VMCB_CR))) {
+		svm_set_efer(&svm->vcpu, vmcb12->save.efer);
+		svm_set_cr0(&svm->vcpu, vmcb12->save.cr0);
+		svm_set_cr4(&svm->vcpu, vmcb12->save.cr4);
+	}
 
 	svm->vcpu.arch.cr2 = vmcb12->save.cr2;
 
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 271196400495..41f5cd1009ca 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1234,7 +1234,7 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
 	svm->asid = 0;
 
 	svm->nested.vmcb12_gpa = 0;
-	svm->nested.last_vmcb12_gpa = 0;
+	svm->nested.last_vmcb12_gpa = -1;
 	vcpu->arch.hflags = 0;
 
 	if (!kvm_pause_in_guest(vcpu->kvm)) {
-- 
2.26.2