linux-kernel - [PATCH v3 2/8] KVM: X86: Go on updating other CPUID leaves when leaf 1 is absent

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Date:   Wed,  8 Jul 2020 14:50:48 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Jim Mattson <jmattson@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>,
        Xiaoyao Li <xiaoyao.li@...el.com>
Subject: [PATCH v3 2/8] KVM: X86: Go on updating other CPUID leaves when leaf 1 is absent

As handling of bits out of leaf 1 added over time, kvm_update_cpuid()
should not return directly if leaf 1 is absent, but should go on
updateing other CPUID leaves.

Keep the update of apic->lapic_timer.timer_mode_mask in a separate
wrapper, to minimize churn for code since it will be moved out of this
function in a future patch.

Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
---
 arch/x86/kvm/cpuid.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 1d13bad42bf9..0e3a23c2ea55 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -60,18 +60,17 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
 	struct kvm_lapic *apic = vcpu->arch.apic;
 
 	best = kvm_find_cpuid_entry(vcpu, 1, 0);
-	if (!best)
-		return 0;
-
-	/* Update OSXSAVE bit */
-	if (boot_cpu_has(X86_FEATURE_XSAVE) && best->function == 0x1)
-		cpuid_entry_change(best, X86_FEATURE_OSXSAVE,
+	if (best) {
+		/* Update OSXSAVE bit */
+		if (boot_cpu_has(X86_FEATURE_XSAVE))
+			cpuid_entry_change(best, X86_FEATURE_OSXSAVE,
 				   kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE));
 
-	cpuid_entry_change(best, X86_FEATURE_APIC,
+		cpuid_entry_change(best, X86_FEATURE_APIC,
 			   vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
+	}
 
-	if (apic) {
+	if (best && apic) {
 		if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
 			apic->lapic_timer.timer_mode_mask = 3 << 17;
 		else
-- 
2.18.4