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

7 files changed, 19 insertions, 21 deletions

diff --git a/tools/testing/selftests/kvm/x86_64/cpuid_test.c b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
index 59dcdf5a1220..96f141a758ca 100644
--- a/tools/testing/selftests/kvm/x86_64/cpuid_test.c
+++ b/tools/testing/selftests/kvm/x86_64/cpuid_test.c
@@ -144,21 +144,22 @@ struct kvm_cpuid2 *vcpu_alloc_cpuid(struct kvm_vm *vm, vm_vaddr_t *p_gva, struct
 	return guest_cpuids;
 }
 
-static void set_cpuid_after_run(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid)
+static void set_cpuid_after_run(struct kvm_vcpu *vcpu)
 {
+	struct kvm_cpuid2 *cpuid = vcpu->cpuid;
 	struct kvm_cpuid_entry2 *ent;
 	int rc;
 	u32 eax, ebx, x;
 
 	/* Setting unmodified CPUID is allowed */
-	rc = __vcpu_set_cpuid(vcpu, cpuid);
+	rc = __vcpu_set_cpuid(vcpu);
 	TEST_ASSERT(!rc, "Setting unmodified CPUID after KVM_RUN failed: %d", rc);
 
 	/* Changing CPU features is forbidden */
 	ent = get_cpuid(cpuid, 0x7, 0);
 	ebx = ent->ebx;
 	ent->ebx--;
-	rc = __vcpu_set_cpuid(vcpu, cpuid);
+	rc = __vcpu_set_cpuid(vcpu);
 	TEST_ASSERT(rc, "Changing CPU features should fail");
 	ent->ebx = ebx;
 
@@ -167,14 +168,14 @@ static void set_cpuid_after_run(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid)
 	eax = ent->eax;
 	x = eax & 0xff;
 	ent->eax = (eax & ~0xffu) | (x - 1);
-	rc = __vcpu_set_cpuid(vcpu, cpuid);
+	rc = __vcpu_set_cpuid(vcpu);
 	TEST_ASSERT(rc, "Changing MAXPHYADDR should fail");
 	ent->eax = eax;
 }
 
 int main(void)
 {
-	struct kvm_cpuid2 *supp_cpuid, *cpuid2;
+	struct kvm_cpuid2 *supp_cpuid;
 	struct kvm_vcpu *vcpu;
 	vm_vaddr_t cpuid_gva;
 	struct kvm_vm *vm;
@@ -183,18 +184,17 @@ int main(void)
 	vm = vm_create_with_one_vcpu(&vcpu, guest_main);
 
 	supp_cpuid = kvm_get_supported_cpuid();
-	cpuid2 = vcpu_get_cpuid(vcpu);
 
-	compare_cpuids(supp_cpuid, cpuid2);
+	compare_cpuids(supp_cpuid, vcpu->cpuid);
 
-	vcpu_alloc_cpuid(vm, &cpuid_gva, cpuid2);
+	vcpu_alloc_cpuid(vm, &cpuid_gva, vcpu->cpuid);
 
 	vcpu_args_set(vcpu, 1, cpuid_gva);
 
 	for (stage = 0; stage < 3; stage++)
 		run_vcpu(vcpu, stage);
 
-	set_cpuid_after_run(vcpu, cpuid2);
+	set_cpuid_after_run(vcpu);
 
 	kvm_vm_free(vm);
 }
diff --git a/tools/testing/selftests/kvm/x86_64/emulator_error_test.c b/tools/testing/selftests/kvm/x86_64/emulator_error_test.c
index 3aa3d17f230f..d8dbed419638 100644
--- a/tools/testing/selftests/kvm/x86_64/emulator_error_test.c
+++ b/tools/testing/selftests/kvm/x86_64/emulator_error_test.c
@@ -171,7 +171,7 @@ int main(int argc, char *argv[])
 	entry->eax = (entry->eax & 0xffffff00) | MAXPHYADDR;
 	set_cpuid(cpuid, entry);
 
-	vcpu_set_cpuid(vcpu, cpuid);
+	vcpu_init_cpuid(vcpu, cpuid);
 
 	rc = kvm_check_cap(KVM_CAP_EXIT_ON_EMULATION_FAILURE);
 	TEST_ASSERT(rc, "KVM_CAP_EXIT_ON_EMULATION_FAILURE is unavailable");
diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_features.c b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
index 2070ba0d6392..86ce1f1e98ee 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_features.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_features.c
@@ -102,7 +102,7 @@ static void hv_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid2 *cpuid,
 		    "failed to set HYPERV_CPUID_ENLIGHTMENT_INFO leaf");
 	TEST_ASSERT(set_cpuid(cpuid, dbg),
 		    "failed to set HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES leaf");
-	vcpu_set_cpuid(vcpu, cpuid);
+	vcpu_init_cpuid(vcpu, cpuid);
 }
 
 static void guest_test_msrs_access(void)
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);
diff --git a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
index c804f6f04134..0ac5bec1e3b7 100644
--- a/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
+++ b/tools/testing/selftests/kvm/x86_64/monitor_mwait_test.c
@@ -80,7 +80,7 @@ int main(int argc, char *argv[])
 	set_cpuid(cpuid, entry);
 
 	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
-	vcpu_set_cpuid(vcpu, cpuid);
+	vcpu_set_cpuid(vcpu);
 
 	run = vcpu->run;
 
diff --git a/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
index 66cb2d0054e6..1cf78ec007f2 100644
--- a/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
+++ b/tools/testing/selftests/kvm/x86_64/vmx_set_nested_state_test.c
@@ -121,7 +121,7 @@ void test_vmx_nested_state(struct kvm_vcpu *vcpu)
 	test_nested_state(vcpu, state);
 
 	/* Enable VMX in the guest CPUID. */
-	vcpu_set_cpuid(vcpu, kvm_get_supported_cpuid());
+	vcpu_set_cpuid(vcpu);
 
 	/*
 	 * Setting vmxon_pa == -1ull and vmcs_pa == -1ull exits early without
@@ -245,7 +245,7 @@ void test_vmx_nested_state(struct kvm_vcpu *vcpu)
 
 void disable_vmx(struct kvm_vcpu *vcpu)
 {
-	struct kvm_cpuid2 *cpuid = kvm_get_supported_cpuid();
+	struct kvm_cpuid2 *cpuid = vcpu->cpuid;
 	int i;
 
 	for (i = 0; i < cpuid->nent; ++i)
@@ -255,7 +255,7 @@ void disable_vmx(struct kvm_vcpu *vcpu)
 	TEST_ASSERT(i != cpuid->nent, "CPUID function 1 not found");
 
 	cpuid->entries[i].ecx &= ~CPUID_VMX;
-	vcpu_set_cpuid(vcpu, cpuid);
+	vcpu_set_cpuid(vcpu);
 	cpuid->entries[i].ecx |= CPUID_VMX;
 }
 
diff --git a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
index 87531623064f..52133bb4d85a 100644
--- a/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xapic_state_test.c
@@ -152,13 +152,13 @@ int main(int argc, char *argv[])
 	vm = vm_create_with_one_vcpu(&x.vcpu, xapic_guest_code);
 	x.is_x2apic = false;
 
-	cpuid = vcpu_get_cpuid(x.vcpu);
+	cpuid = x.vcpu->cpuid;
 	for (i = 0; i < cpuid->nent; i++) {
 		if (cpuid->entries[i].function == 1)
 			break;
 	}
 	cpuid->entries[i].ecx &= ~BIT(21);
-	vcpu_set_cpuid(x.vcpu, cpuid);
+	vcpu_set_cpuid(x.vcpu);
 
 	virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
 	test_icr(&x);