linux-kernel - [PATCH v3 04/15] KVM: VMX: Check KVM CPU caps, not just VMX MSR support, for XSAVE enabling

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Message-ID: <20230815203653.519297-5-seanjc@google.com>
Date:   Tue, 15 Aug 2023 13:36:42 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zeng Guang <guang.zeng@...el.com>,
        Yuan Yao <yuan.yao@...el.com>
Subject: [PATCH v3 04/15] KVM: VMX: Check KVM CPU caps, not just VMX MSR
 support, for XSAVE enabling

Check KVM CPU capabilities instead of raw VMX support for XSAVES when
determining whether or not XSAVER can/should be exposed to the guest.
Practically speaking, it's nonsensical/impossible for a CPU to support
"enable XSAVES" without XSAVES being supported natively.  The real
motivation for checking kvm_cpu_cap_has() is to allow using the governed
feature's standard check-and-set logic.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 1bf85bd53416..78f292b7e2c5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7745,7 +7745,7 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 	 * to the guest.  XSAVES depends on CR4.OSXSAVE, and CR4.OSXSAVE can be
 	 * set if and only if XSAVE is supported.
 	 */
-	vcpu->arch.xsaves_enabled = cpu_has_vmx_xsaves() &&
+	vcpu->arch.xsaves_enabled = kvm_cpu_cap_has(X86_FEATURE_XSAVES) &&
 				    boot_cpu_has(X86_FEATURE_XSAVE) &&
 				    guest_cpuid_has(vcpu, X86_FEATURE_XSAVE) &&
 				    guest_cpuid_has(vcpu, X86_FEATURE_XSAVES);
-- 
2.41.0.694.ge786442a9b-goog