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

Fred Griffoul
2025-01-22T16:16:35Z

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@amazon.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