linux-kernel - [PATCH] KVM: x86: Update Xen-specific CPUID leaves during mangling

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Message-ID: <20250122161612.20981-1-fgriffo@amazon.co.uk>
Date: Wed, 22 Jan 2025 16:16:11 +0000
From: Fred Griffoul <fgriffo@...zon.co.uk>
To: <kvm@...r.kernel.org>
CC: Fred Griffoul <fgriffo@...zon.co.uk>, Sean Christopherson
	<seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, <x86@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, David Woodhouse <dwmw2@...radead.org>,
	"Paul Durrant" <paul@....org>, Vitaly Kuznetsov <vkuznets@...hat.com>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH] KVM: x86: Update Xen-specific CPUID leaves during mangling

Previous commit ee3a5f9e3d9b ("KVM: x86: Do runtime CPUID update before
updating vcpu->arch.cpuid_entries") implemented CPUID data mangling in
KVM_SET_CPUID2 support before verifying that no changes occur on running
vCPUs. However, it overlooked the CPUID leaves that are modified by
KVM's Xen emulation.

Fix this by calling a Xen update function when mangling CPUID data.

Fixes: ee3a5f9e3d9b ("KVM: x86: Do runtime CPUID update before updating vcpu->arch.cpuid_entries")
Signed-off-by: Fred Griffoul <fgriffo@...zon.co.uk>
---
 arch/x86/kvm/cpuid.c | 1 +
 arch/x86/kvm/xen.c   | 5 +++++
 arch/x86/kvm/xen.h   | 5 +++++
 3 files changed, 11 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index edef30359c19..432d8e9e1bab 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -212,6 +212,7 @@ static int kvm_cpuid_check_equal(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2
 	 */
 	kvm_update_cpuid_runtime(vcpu);
 	kvm_apply_cpuid_pv_features_quirk(vcpu);
+	kvm_xen_update_cpuid_runtime(vcpu);
 
 	if (nent != vcpu->arch.cpuid_nent)
 		return -EINVAL;
diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index a909b817b9c0..219f9a9a92be 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -2270,6 +2270,11 @@ void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu)
 		entry->eax = vcpu->arch.hw_tsc_khz;
 }
 
+void kvm_xen_update_cpuid_runtime(struct kvm_vcpu *vcpu)
+{
+	kvm_xen_update_tsc_info(vcpu);
+}
+
 void kvm_xen_init_vm(struct kvm *kvm)
 {
 	mutex_init(&kvm->arch.xen.xen_lock);
diff --git a/arch/x86/kvm/xen.h b/arch/x86/kvm/xen.h
index f5841d9000ae..d3182b0ab7e3 100644
--- a/arch/x86/kvm/xen.h
+++ b/arch/x86/kvm/xen.h
@@ -36,6 +36,7 @@ int kvm_xen_setup_evtchn(struct kvm *kvm,
 			 struct kvm_kernel_irq_routing_entry *e,
 			 const struct kvm_irq_routing_entry *ue);
 void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu);
+void kvm_xen_update_cpuid_runtime(struct kvm_vcpu *vcpu);
 
 static inline void kvm_xen_sw_enable_lapic(struct kvm_vcpu *vcpu)
 {
@@ -160,6 +161,10 @@ static inline bool kvm_xen_timer_enabled(struct kvm_vcpu *vcpu)
 static inline void kvm_xen_update_tsc_info(struct kvm_vcpu *vcpu)
 {
 }
+
+static inline void kvm_xen_update_cpuid_runtime(struct kvm_vcpu *vcpu)
+{
+}
 #endif
 
 int kvm_xen_hypercall(struct kvm_vcpu *vcpu);
-- 
2.40.1