linux-kernel - [PATCH 8/9] KVM: SVM: Don't manually emulate RDPMC if nrips=0

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Date:   Thu,  4 Feb 2021 16:57:49 -0800
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Jiri Kosina <trivial@...nel.org>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 8/9] KVM: SVM: Don't manually emulate RDPMC if nrips=0

Remove bizarre code that causes KVM to run RDPMC through the emulator
when nrips is disabled.  Accelerated emulation of RDPMC doesn't rely on
any additional data from the VMCB, and SVM has generic handling for
updating RIP to skip instructions when nrips is disabled.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/svm/svm.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 74f37f282050..b6acc73d356a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2434,14 +2434,6 @@ static int rsm_interception(struct kvm_vcpu *vcpu)
 	return kvm_emulate_instruction_from_buffer(vcpu, rsm_ins_bytes, 2);
 }
 
-static int rdpmc_interception(struct kvm_vcpu *vcpu)
-{
-	if (!nrips)
-		return emulate_on_interception(vcpu);
-
-	return kvm_emulate_rdpmc(vcpu);
-}
-
 static bool check_selective_cr0_intercepted(struct kvm_vcpu *vcpu,
 					    unsigned long val)
 {
@@ -3068,7 +3060,7 @@ static int (*const svm_exit_handlers[])(struct kvm_vcpu *vcpu) = {
 	[SVM_EXIT_SMI]				= kvm_emulate_as_nop,
 	[SVM_EXIT_INIT]				= kvm_emulate_as_nop,
 	[SVM_EXIT_VINTR]			= interrupt_window_interception,
-	[SVM_EXIT_RDPMC]			= rdpmc_interception,
+	[SVM_EXIT_RDPMC]			= kvm_emulate_rdpmc,
 	[SVM_EXIT_CPUID]			= kvm_emulate_cpuid,
 	[SVM_EXIT_IRET]                         = iret_interception,
 	[SVM_EXIT_INVD]                         = kvm_emulate_invd,
-- 
2.30.0.365.g02bc693789-goog