Commit ee3a5f9e3d9b ("KVM: x86: Do runtime CPUID update before updating
vcpu->arch.cpuid_entries") moved tweaking of the supplied CPUID
data earlier in kvm_set_cpuid() but __kvm_update_cpuid_runtime() actually
uses 'vcpu->arch.kvm_cpuid' (though __kvm_find_kvm_cpuid_features()) which
gets set later in kvm_set_cpuid(). In some cases, e.g. when kvm_set_cpuid()
is called for the first time and 'vcpu->arch.kvm_cpuid' is clear,
__kvm_find_kvm_cpuid_features() fails to find KVM PV feature entry and the
logic which clears KVM_FEATURE_PV_UNHALT after enabling
KVM_X86_DISABLE_EXITS_HLT does not work.
The logic, introduced by the commit ee3a5f9e3d9b ("KVM: x86: Do runtime
CPUID update before updating vcpu->arch.cpuid_entries") must stay: the
supplied CPUID data is tweaked by KVM first (__kvm_update_cpuid_runtime())
and checked later (kvm_check_cpuid()) and the actual data
(vcpu->arch.cpuid_*, vcpu->arch.kvm_cpuid, vcpu->arch.xen.cpuid,..) is only
updated on success.
Switch to searching for KVM_SIGNATURE in the supplied CPUID data to
discover KVM PV feature entry instead of using stale 'vcpu->arch.kvm_cpuid'.
While on it, drop pointless "&& (best->eax & (1 << KVM_FEATURE_PV_UNHALT)"
check when clearing KVM_FEATURE_PV_UNHALT bit.
Fixes: ee3a5f9e3d9b ("KVM: x86: Do runtime CPUID update before updating vcpu->arch.cpuid_entries")
Reported-and-tested-by: Li RongQing <lirongqing@xxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/kvm/cpuid.c | 31 +++++++++++++++++--------------
1 file changed, 17 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 0e1e3e5df6dd..bfc0bfcb2bc6 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -224,22 +224,22 @@ static struct kvm_hypervisor_cpuid kvm_get_hypervisor_cpuid(struct kvm_vcpu *vcp
vcpu->arch.cpuid_nent, sig);
}
-static struct kvm_cpuid_entry2 *__kvm_find_kvm_cpuid_features(struct kvm_vcpu *vcpu,
- struct kvm_cpuid_entry2 *entries, int nent)
+static struct kvm_cpuid_entry2 *__kvm_find_kvm_cpuid_features(struct kvm_cpuid_entry2 *entries,
+ int nent, u32 kvm_cpuid_base)
{
- u32 base = vcpu->arch.kvm_cpuid.base;
-
- if (!base)
- return NULL;
-
- return cpuid_entry2_find(entries, nent, base | KVM_CPUID_FEATURES,
+ return cpuid_entry2_find(entries, nent, kvm_cpuid_base | KVM_CPUID_FEATURES,
KVM_CPUID_INDEX_NOT_SIGNIFICANT);
}
static struct kvm_cpuid_entry2 *kvm_find_kvm_cpuid_features(struct kvm_vcpu *vcpu)
{
- return __kvm_find_kvm_cpuid_features(vcpu, vcpu->arch.cpuid_entries,
- vcpu->arch.cpuid_nent);
+ u32 base = vcpu->arch.kvm_cpuid.base;
+
+ if (!base)
+ return NULL;
+
+ return __kvm_find_kvm_cpuid_features(vcpu->arch.cpuid_entries,
+ vcpu->arch.cpuid_nent, base);
}
void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
@@ -273,6 +273,7 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
int nent)
{
struct kvm_cpuid_entry2 *best;
+ struct kvm_hypervisor_cpuid kvm_cpuid;
best = cpuid_entry2_find(entries, nent, 1, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
if (best) {
@@ -299,10 +300,12 @@ static void __kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu, struct kvm_cpuid_e
cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
- best = __kvm_find_kvm_cpuid_features(vcpu, entries, nent);
- if (kvm_hlt_in_guest(vcpu->kvm) && best &&
- (best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
- best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
+ kvm_cpuid = __kvm_get_hypervisor_cpuid(entries, nent, KVM_SIGNATURE);
+ if (kvm_cpuid.base) {
+ best = __kvm_find_kvm_cpuid_features(entries, nent, kvm_cpuid.base);
+ if (kvm_hlt_in_guest(vcpu->kvm) && best)
+ best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
+ }
if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {
best = cpuid_entry2_find(entries, nent, 0x1, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
--
2.43.0
