linux-kernel - [PATCH] KVM: x86/pmu: Remove redundant check for MSR_IA32_DS

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Date:   Tue, 11 Apr 2023 21:03:38 +0800
From:   Jinrong Liang <ljr.kernel@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Like Xu <like.xu.linux@...il.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: x86/pmu: Remove redundant check for MSR_IA32_DS_AREA set handler

From: Jinrong Liang <cloudliang@...cent.com>

After commit 2de154f541fc ("KVM: x86/pmu: Provide "error" semantics
for unsupported-but-known PMU MSRs"), the guest_cpuid_has(DS) check
is not necessary any more since if the guest supports X86_FEATURE_DS,
it never returns 1. And if the guest does not support this feature,
the set_msr handler will get false from kvm_pmu_is_valid_msr() before
reaching this point. Therefore, the check will not be true in all cases
and can be safely removed, which also simplifies the code and improves
its readability.

Signed-off-by: Jinrong Liang <cloudliang@...cent.com>
---
 arch/x86/kvm/vmx/pmu_intel.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index e8a3be0b9df9..b0d70a8b7613 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -443,8 +443,6 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		}
 		break;
 	case MSR_IA32_DS_AREA:
-		if (msr_info->host_initiated && data && !guest_cpuid_has(vcpu, X86_FEATURE_DS))
-			return 1;
 		if (is_noncanonical_address(data, vcpu))
 			return 1;
 		pmu->ds_area = data;
-- 
2.31.1