KVM: selftests: Cache CPUID in struct kvm_vcpu

Cache a vCPU's CPUID information in "struct kvm_vcpu" to allow fixing the
mess where tests, often unknowingly, modify the global/static "cpuid"
allocated by kvm_get_supported_cpuid().

Add vcpu_init_cpuid() to handle stuffing an entirely different CPUID
model, e.g. during vCPU creation or when switching to the Hyper-V enabled
CPUID model.  Automatically refresh the cache on vcpu_set_cpuid() so that
any adjustments made by KVM are always reflected in the cache.  Drop
vcpu_get_cpuid() entirely to force tests to use the cache, and to allow
adding e.g. vcpu_get_cpuid_entry() in the future without creating a
conflicting set of APIs where vcpu_get_cpuid() does KVM_GET_CPUID2, but
vcpu_get_cpuid_entry() does not.

Opportunistically convert the VMX nested state test and KVM PV test to
manipulating the vCPU's CPUID (because it's easy), but use
vcpu_init_cpuid() for the Hyper-V features test and "emulator error" test
to effectively retain their current behavior as they're less trivial to
convert.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20220614200707.3315957-19-seanjc@google.com

1 files changed, 2 insertions, 4 deletions

diff --git a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
index ea452444f4af..986ca7282a09 100644
--- a/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvm_pv_test.c
@@ -147,7 +147,6 @@ static void enter_guest(struct kvm_vcpu *vcpu)
 
 int main(void)
 {
-	struct kvm_cpuid2 *best;
 	struct kvm_vcpu *vcpu;
 	struct kvm_vm *vm;
 
@@ -157,9 +156,8 @@ int main(void)
 
 	vcpu_enable_cap(vcpu, KVM_CAP_ENFORCE_PV_FEATURE_CPUID, 1);
 
-	best = kvm_get_supported_cpuid();
-	clear_kvm_cpuid_features(best);
-	vcpu_set_cpuid(vcpu, best);
+	clear_kvm_cpuid_features(vcpu->cpuid);
+	vcpu_set_cpuid(vcpu);
 
 	vm_init_descriptor_tables(vm);
 	vcpu_init_descriptor_tables(vcpu);