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Fix a bug in KVM_SET_CPUID{2,} where KVM looks at the wrong CPUID entries (old

Browse Source 
vs. new) and ultimately neglects to clear PV_UNHALT from vCPUs with HLT-exiting
 disabled.
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Merge tag 'kvm-x86-pvunhalt-6.9' of https://github.com/kvm-x86/linux into HEAD

Fix a bug in KVM_SET_CPUID{2,} where KVM looks at the wrong CPUID entries (old
vs. new) and ultimately neglects to clear PV_UNHALT from vCPUs with HLT-exiting
disabled.
This commit is contained in:
Paolo Bonzini 2024-03-18 19:19:08 -04:00
commit 0d1756482e
3 changed files with 77 additions and 17 deletions
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44
arch/x86/kvm/cpuid.c
View File

@ -189,15 +189,15 @@ static int kvm_cpuid_check_equal(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2
return 0;
}
static struct kvm_hypervisor_cpuid kvm_get_hypervisor_cpuid(struct kvm_vcpu *vcpu,
const char *sig)
static struct kvm_hypervisor_cpuid __kvm_get_hypervisor_cpuid(struct kvm_cpuid_entry2 *entries,
int nent, const char *sig)
{
struct kvm_hypervisor_cpuid cpuid = {};
struct kvm_cpuid_entry2 *entry;
u32 base;
for_each_possible_hypervisor_cpuid_base(base) {
entry = kvm_find_cpuid_entry(vcpu, base);
entry = cpuid_entry2_find(entries, nent, base, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
if (entry) {
u32 signature[3];
@ -217,22 +217,29 @@ static struct kvm_hypervisor_cpuid kvm_get_hypervisor_cpuid(struct kvm_vcpu *vcp
return cpuid;
}
static struct kvm_cpuid_entry2 *__kvm_find_kvm_cpuid_features(struct kvm_vcpu *vcpu,
struct kvm_cpuid_entry2 *entries, int nent)
static struct kvm_hypervisor_cpuid kvm_get_hypervisor_cpuid(struct kvm_vcpu *vcpu,
const char *sig)
{
return __kvm_get_hypervisor_cpuid(vcpu->arch.cpuid_entries,
vcpu->arch.cpuid_nent, sig);
}
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)
@ -266,6 +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) {
@ -292,10 +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);

11
tools/testing/selftests/kvm/include/x86_64/processor.h
View File

@ -1037,8 +1037,19 @@ static inline void vcpu_set_cpuid(struct kvm_vcpu *vcpu)
void vcpu_set_cpuid_property(struct kvm_vcpu *vcpu,
struct kvm_x86_cpu_property property,
uint32_t value);
void vcpu_set_cpuid_maxphyaddr(struct kvm_vcpu *vcpu, uint8_t maxphyaddr);
void vcpu_clear_cpuid_entry(struct kvm_vcpu *vcpu, uint32_t function);
static inline bool vcpu_cpuid_has(struct kvm_vcpu *vcpu,
struct kvm_x86_cpu_feature feature)
{
struct kvm_cpuid_entry2 *entry;
entry = __vcpu_get_cpuid_entry(vcpu, feature.function, feature.index);
return *((&entry->eax) + feature.reg) & BIT(feature.bit);
}
void vcpu_set_or_clear_cpuid_feature(struct kvm_vcpu *vcpu,
struct kvm_x86_cpu_feature feature,
bool set);

39
tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
View File

@ -133,6 +133,43 @@ static void enter_guest(struct kvm_vcpu *vcpu)
}
}
static void test_pv_unhalt(void)
{
struct kvm_vcpu *vcpu;
struct kvm_vm *vm;
struct kvm_cpuid_entry2 *ent;
u32 kvm_sig_old;
pr_info("testing KVM_FEATURE_PV_UNHALT\n");
TEST_REQUIRE(KVM_CAP_X86_DISABLE_EXITS);
/* KVM_PV_UNHALT test */
vm = vm_create_with_one_vcpu(&vcpu, guest_main);
vcpu_set_cpuid_feature(vcpu, X86_FEATURE_KVM_PV_UNHALT);
TEST_ASSERT(vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
"Enabling X86_FEATURE_KVM_PV_UNHALT had no effect");
/* Make sure KVM clears vcpu->arch.kvm_cpuid */
ent = vcpu_get_cpuid_entry(vcpu, KVM_CPUID_SIGNATURE);
kvm_sig_old = ent->ebx;
ent->ebx = 0xdeadbeef;
vcpu_set_cpuid(vcpu);
vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS, KVM_X86_DISABLE_EXITS_HLT);
ent = vcpu_get_cpuid_entry(vcpu, KVM_CPUID_SIGNATURE);
ent->ebx = kvm_sig_old;
vcpu_set_cpuid(vcpu);
TEST_ASSERT(!vcpu_cpuid_has(vcpu, X86_FEATURE_KVM_PV_UNHALT),
"KVM_FEATURE_PV_UNHALT is set with KVM_CAP_X86_DISABLE_EXITS");
/* FIXME: actually test KVM_FEATURE_PV_UNHALT feature */
kvm_vm_free(vm);
}
int main(void)
{
struct kvm_vcpu *vcpu;
@ -151,4 +188,6 @@ int main(void)
enter_guest(vcpu);
kvm_vm_free(vm);
test_pv_unhalt();
}