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KVM: x86: Use actual kvm_cpuid.base for clearing KVM_FEATURE_PV_UNHALT 

commit 4736d85f0d18ad0469439a0ebc7ccb0cd94bd754 upstream.

Commit ee3a5f9e3d ("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 ee3a5f9e3d ("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: ee3a5f9e3d ("KVM: x86: Do runtime CPUID update before updating vcpu->arch.cpuid_entries")
Reported-and-tested-by: Li RongQing <lirongqing@baidu.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20240228101837.93642-3-vkuznets@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
This commit is contained in:
Vitaly Kuznetsov 2024-02-28 11:18:36 +01:00 committed by Like Xu
parent 52f0e467d0
commit 9f2a5e8722
1 changed files with 17 additions and 14 deletions
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31
arch/x86/kvm/cpuid.c
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@ -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)
{
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)
{
u32 base = vcpu->arch.kvm_cpuid.base;
if (!base)
return NULL;
return cpuid_entry2_find(entries, nent, 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);
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);