linux-kernel - [PATCH v2 15/49] KVM: x86: Zero out PV features cache when the CPUID leaf is not present

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Message-ID: <20240517173926.965351-16-seanjc@google.com>
Date: Fri, 17 May 2024 10:38:52 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Hou Wenlong <houwenlong.hwl@...group.com>, Kechen Lu <kechenl@...dia.com>, 
	Oliver Upton <oliver.upton@...ux.dev>, Maxim Levitsky <mlevitsk@...hat.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Yang Weijiang <weijiang.yang@...el.com>, 
	Robert Hoo <robert.hoo.linux@...il.com>
Subject: [PATCH v2 15/49] KVM: x86: Zero out PV features cache when the CPUID
 leaf is not present

Clear KVM's PV feature cache prior when processing a new guest CPUID so
that KVM doesn't keep a stale cache entry if userspace does KVM_SET_CPUID2
multiple times, once with a PV features entry, and a second time without.

Fixes: 66570e966dd9 ("kvm: x86: only provide PV features if enabled in guest's CPUID")
Cc: Oliver Upton <oliver.upton@...ux.dev>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/cpuid.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index f756a91a3f2f..be1c8f43e090 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -246,6 +246,8 @@ void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpuid_entry2 *best = kvm_find_kvm_cpuid_features(vcpu);
 
+	vcpu->arch.pv_cpuid.features = 0;
+
 	/*
 	 * save the feature bitmap to avoid cpuid lookup for every PV
 	 * operation
-- 
2.45.0.215.g3402c0e53f-goog