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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>,
	Junaid Shahid <junaids@google.com>,
	linux-kernel@vger.kernel.org
Subject: [PATCH v4 8/9] KVM: nSVM: use nested_svm_load_cr3() on guest->host switch
Date: Fri, 10 Jul 2020 16:11:56 +0200	[thread overview]
Message-ID: <20200710141157.1640173-9-vkuznets@redhat.com> (raw)
In-Reply-To: <20200710141157.1640173-1-vkuznets@redhat.com>

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@redhat.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 219871752dc5..434e527096b7 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,
@@ -651,15 +651,12 @@ 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


  parent reply	other threads:[~2020-07-10 14:12 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-10 14:11 [PATCH v4 0/9] KVM: nSVM: fixes for CR3/MMU switch upon nested guest entry/exit Vitaly Kuznetsov
2020-07-10 14:11 ` [PATCH v4 1/9] KVM: nSVM: split kvm_init_shadow_npt_mmu() from kvm_init_shadow_mmu() Vitaly Kuznetsov
2020-07-10 14:11 ` [PATCH v4 2/9] KVM: MMU: stop dereferencing vcpu->arch.mmu to get the context for MMU init Vitaly Kuznetsov
2020-07-10 14:11 ` [PATCH v4 3/9] KVM: nSVM: reset nested_run_pending upon nested_svm_vmrun_msrpm() failure Vitaly Kuznetsov
2020-07-10 14:11 ` [PATCH v4 4/9] KVM: nSVM: prepare to handle errors from enter_svm_guest_mode() Vitaly Kuznetsov
2020-07-10 14:11 ` [PATCH v4 5/9] KVM: nSVM: introduce nested_svm_load_cr3()/nested_npt_enabled() Vitaly Kuznetsov
2020-07-13 22:38   ` Sean Christopherson
2020-07-14 11:26     ` Vitaly Kuznetsov
2020-07-15  4:36       ` Sean Christopherson
2020-07-10 14:11 ` [PATCH v4 6/9] KVM: nSVM: move kvm_set_cr3() after nested_svm_uninit_mmu_context() Vitaly Kuznetsov
2020-07-10 14:11 ` [PATCH v4 7/9] KVM: nSVM: implement nested_svm_load_cr3() and use it for host->guest switch Vitaly Kuznetsov
2020-07-10 14:11 ` Vitaly Kuznetsov [this message]
2020-07-10 14:11 ` [PATCH v4 9/9] KVM: x86: drop superfluous mmu_check_root() from fast_pgd_switch() Vitaly Kuznetsov
2020-07-10 17:03 ` [PATCH v4 0/9] KVM: nSVM: fixes for CR3/MMU switch upon nested guest entry/exit Paolo Bonzini

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