linux-kernel - [PATCH 18/23] KVM: SVM: Don't manually emulate RDPMC if nrips=0

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Date:   Tue,  2 Mar 2021 14:33:38 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     seanjc@...gle.com
Subject: [PATCH 18/23] KVM: SVM: Don't manually emulate RDPMC if nrips=0

From: Sean Christopherson <seanjc@...gle.com>

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>
Message-Id: <20210205005750.3841462-9-seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.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 8cb31603bce5..3725a4636930 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2424,14 +2424,6 @@ 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)
 {
@@ -3058,7 +3050,7 @@ 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,
-- 
2.26.2