[PATCH] KVM: x86/pmu: Remove redundant check for MSR_IA32_DS_AREA set handler

[PATCH] KVM: x86/pmu: Remove redundant check for MSR_IA32_DS_AREA set handler

[Jinrong Liang]

From: Jinrong Liang <cloudliang@tencent.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@tencent.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

Re: [PATCH] KVM: x86/pmu: Remove redundant check for MSR_IA32_DS_AREA set handler

[Sean Christopherson]

On Tue, 11 Apr 2023 21:03:38 +0800, Jinrong Liang wrote:
> 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.
> 
> [...]

Applied to kvm-x86 vmx, thanks!

[1/1] KVM: x86/pmu: Remove redundant check for MSR_IA32_DS_AREA set handler
      https://github.com/kvm-x86/linux/commit/33ab767c2628

--
https://github.com/kvm-x86/linux/tree/next
https://github.com/kvm-x86/linux/tree/fixes