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KVM: selftests: Manage CPUID array in Hyper-V CPUID test's core helper

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Allocate, get, and free the CPUID array in the Hyper-V CPUID test in the
test's core helper, instead of copy+pasting code at each call site.  In
addition to deduplicating a small amount of code, restricting visibility
of the array to a single invocation of the core test prevents "leaking" an
array across test cases.  Passing in @vcpu to the helper will also allow
pivoting on VM-scoped information without needing to pass more booleans,
e.g. to conditionally assert on features that require an in-kernel APIC.

To avoid use-after-free bugs due to overzealous and careless developers,
opportunstically add a comment to explain that the system-scoped helper
caches the Hyper-V CPUID entries, i.e. that the caller is not responsible
for freeing the memory.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Link: https://lore.kernel.org/r/20250118003454.2619573-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2025-01-17 16:34:53 -08:00
parent 0b6db0dc43
commit cd5a0c2f0f
1 changed files with 17 additions and 13 deletions
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30
tools/testing/selftests/kvm/x86/hyperv_cpuid.c
View file

@ -41,13 +41,18 @@ static bool smt_possible(void)
return res; return res;
} }
static void test_hv_cpuid(const struct kvm_cpuid2 *hv_cpuid_entries, static void test_hv_cpuid(struct kvm_vcpu *vcpu, bool evmcs_expected)
bool evmcs_expected)
{ {
const struct kvm_cpuid2 *hv_cpuid_entries;
int i; int i;
int nent_expected = 10; int nent_expected = 10;
u32 test_val; u32 test_val;
if (vcpu)
hv_cpuid_entries = vcpu_get_supported_hv_cpuid(vcpu);
else
hv_cpuid_entries = kvm_get_supported_hv_cpuid();
TEST_ASSERT(hv_cpuid_entries->nent == nent_expected, TEST_ASSERT(hv_cpuid_entries->nent == nent_expected,
"KVM_GET_SUPPORTED_HV_CPUID should return %d entries" "KVM_GET_SUPPORTED_HV_CPUID should return %d entries"
" (returned %d)", " (returned %d)",
@ -109,6 +114,13 @@ static void test_hv_cpuid(const struct kvm_cpuid2 *hv_cpuid_entries,
* entry->edx); * entry->edx);
*/ */
} }
/*
* Note, the CPUID array returned by the system-scoped helper is a one-
* time allocation, i.e. must not be freed.
*/
if (vcpu)
free((void *)hv_cpuid_entries);
} }
static void test_hv_cpuid_e2big(struct kvm_vm *vm, struct kvm_vcpu *vcpu) static void test_hv_cpuid_e2big(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
@ -129,7 +141,6 @@ static void test_hv_cpuid_e2big(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
int main(int argc, char *argv[]) int main(int argc, char *argv[])
{ {
struct kvm_vm *vm; struct kvm_vm *vm;
const struct kvm_cpuid2 *hv_cpuid_entries;
struct kvm_vcpu *vcpu; struct kvm_vcpu *vcpu;
TEST_REQUIRE(kvm_has_cap(KVM_CAP_HYPERV_CPUID)); TEST_REQUIRE(kvm_has_cap(KVM_CAP_HYPERV_CPUID));
@ -138,10 +149,7 @@ int main(int argc, char *argv[])
/* Test vCPU ioctl version */ /* Test vCPU ioctl version */
test_hv_cpuid_e2big(vm, vcpu); test_hv_cpuid_e2big(vm, vcpu);
test_hv_cpuid(vcpu, false);
hv_cpuid_entries = vcpu_get_supported_hv_cpuid(vcpu);
test_hv_cpuid(hv_cpuid_entries, false);
free((void *)hv_cpuid_entries);
if (!kvm_cpu_has(X86_FEATURE_VMX) || if (!kvm_cpu_has(X86_FEATURE_VMX) ||
!kvm_has_cap(KVM_CAP_HYPERV_ENLIGHTENED_VMCS)) { !kvm_has_cap(KVM_CAP_HYPERV_ENLIGHTENED_VMCS)) {
@ -149,9 +157,7 @@ int main(int argc, char *argv[])
goto do_sys; goto do_sys;
} }
vcpu_enable_evmcs(vcpu); vcpu_enable_evmcs(vcpu);
hv_cpuid_entries = vcpu_get_supported_hv_cpuid(vcpu); test_hv_cpuid(vcpu, true);
test_hv_cpuid(hv_cpuid_entries, true);
free((void *)hv_cpuid_entries);
do_sys: do_sys:
/* Test system ioctl version */ /* Test system ioctl version */
@ -161,9 +167,7 @@ do_sys:
} }
test_hv_cpuid_e2big(vm, NULL); test_hv_cpuid_e2big(vm, NULL);
test_hv_cpuid(NULL, kvm_cpu_has(X86_FEATURE_VMX));
hv_cpuid_entries = kvm_get_supported_hv_cpuid();
test_hv_cpuid(hv_cpuid_entries, kvm_cpu_has(X86_FEATURE_VMX));
out: out:
kvm_vm_free(vm); kvm_vm_free(vm);