linux-kernel - [PATCH v2 65/66] KVM: nSVM: Advertise and enable NRIPS for L1 iff nrips is enabled

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Date:   Mon,  2 Mar 2020 15:57:08 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.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, Xiaoyao Li <xiaoyao.li@...el.com>
Subject: [PATCH v2 65/66] KVM: nSVM: Advertise and enable NRIPS for L1 iff nrips is enabled

Set NRIPS in KVM capabilities if and only if nrips=true, which naturally
incorporates the boot_cpu_has() check, and set nrips_enabled only if the
KVM capability is enabled.

Note, previously KVM would set nrips_enabled based purely on userspace
input, but at worst that would cause KVM to propagate garbage into L1,
i.e. userspace would simply be hosing its VM.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/svm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8e39dcd3160d..32d9c13ec6b9 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1377,7 +1377,7 @@ static __init void svm_set_cpu_caps(void)
 	if (nested) {
 		kvm_cpu_cap_set(X86_FEATURE_SVM);
 
-		if (boot_cpu_has(X86_FEATURE_NRIPS))
+		if (nrips)
 			kvm_cpu_cap_set(X86_FEATURE_NRIPS);
 
 		if (npt_enabled)
@@ -6031,7 +6031,8 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
 				    boot_cpu_has(X86_FEATURE_XSAVES);
 
 	/* Update nrips enabled cache */
-	svm->nrips_enabled = !!guest_cpuid_has(&svm->vcpu, X86_FEATURE_NRIPS);
+	svm->nrips_enabled = kvm_cpu_cap_has(X86_FEATURE_NRIPS) &&
+			     guest_cpuid_has(&svm->vcpu, X86_FEATURE_NRIPS);
 
 	if (!kvm_vcpu_apicv_active(vcpu))
 		return;
-- 
2.24.1