linux-kernel - [PATCH v3 8/9] KVM: nSVM: use nested_svm_load

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Date:   Thu,  9 Jul 2020 16:53:57 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 8/9] KVM: nSVM: use nested_svm_load_cr3() on guest->host switch

Make nSVM code resemble nVMX where nested_vmx_load_cr3() is used on
both guest->host and host->guest transitions. Also, we can now
eliminate unconditional kvm_mmu_reset_context() and speed things up.

Note, nVMX has two different paths: load_vmcs12_host_state() and
nested_vmx_restore_host_state() and the later is used to restore from
'partial' switch to L2, it always uses kvm_mmu_reset_context().
nSVM doesn't have this yet. Also, nested_svm_vmexit()'s return value
is almost always ignored nowadays.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/svm/nested.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 5ddf20941cf9..9a137d3b3a1c 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -317,7 +317,7 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm)
 }
 
 /*
- * Load guest's cr3 at nested entry. @nested_npt is true if we are
+ * Load guest's/host's cr3 at nested entry. @nested_npt is true if we are
  * emulating VM-Entry into a guest with NPT enabled.
  */
 static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
@@ -658,15 +658,12 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
 
 	nested_svm_uninit_mmu_context(&svm->vcpu);
 
-	if (npt_enabled) {
-		svm->vmcb->save.cr3 = hsave->save.cr3;
-		svm->vcpu.arch.cr3 = hsave->save.cr3;
-	} else {
-		(void)kvm_set_cr3(&svm->vcpu, hsave->save.cr3);
-	}
+	rc = nested_svm_load_cr3(&svm->vcpu, hsave->save.cr3, false);
+	if (rc)
+		return 1;
 
-	kvm_mmu_reset_context(&svm->vcpu);
-	kvm_mmu_load(&svm->vcpu);
+	if (npt_enabled)
+		svm->vmcb->save.cr3 = hsave->save.cr3;
 
 	/*
 	 * Drop what we picked up for L2 via svm_complete_interrupts() so it
-- 
2.25.4