[v3,09/10] KVM: selftests: Expect #PF(RSVD) when TDP is disabled

Commit Message

David Matlack Oct. 31, 2022, 6 p.m. UTC

Change smaller_maxphyaddr_emulation_test to expect a #PF(RSVD), rather
than an emulation failure, when TDP is disabled. KVM only needs to
emulate instructions to emulate a smaller guest.MAXPHYADDR when TDP is
enabled.

Fixes: 39bbcc3a4e39 ("selftests: kvm: Allows userspace to handle emulation errors.")
Signed-off-by: David Matlack <[e-mail]>
---
 .../smaller_maxphyaddr_emulation_test.c       | 47 ++++++++++++++++---
 1 file changed, 41 insertions(+), 6 deletions(-)

Comments

Sean Christopherson Oct. 31, 2022, 6:07 p.m. UTC | #1

On Mon, Oct 31, 2022, David Matlack wrote:
> -static void guest_code(void)
> +static void guest_code(bool tdp_enabled)
>  {
> -	flds(MEM_REGION_GVA);
> +	uint64_t error_code;
> +	uint64_t vector;
> +
> +	vector = kvm_asm_safe_ec(FLDS_MEM_EAX, error_code, "a"(MEM_REGION_GVA));
> +
> +	/*
> +	 * When TDP is disabled, no instruction emulation is required so flds
> +	 * should generate #PF(RSVD).
> +	 */
> +	if (!tdp_enabled) {
> +		GUEST_ASSERT_EQ(vector, PF_VECTOR);
> +		GUEST_ASSERT(error_code & PFERR_RSVD_MASK);
> +	}

Probably worth adding

	} else {
		GUEST_ASSERT(!vector);
	}

to verify no fault occurs in the emulation case?  Or to avoid the inverted check,

	if (tdp_enabled) {
		GUEST_ASSERT(!vector);
	} else {
		GUEST_ASSERT_EQ(vector, PF_VECTOR);
		GUEST_ASSERT(error_code & PFERR_RSVD_MASK);
	}

It's mostly redundant with assert_exit_for_flds_emulation_failure(), but at worst
it'll help docuemnts the expected behavior in the TDP case.

Patch

diff --git a/tools/testing/selftests/kvm/x86_64/smaller_maxphyaddr_emulation_test.c b/tools/testing/selftests/kvm/x86_64/smaller_maxphyaddr_emulation_test.c
index f438a98e8bb7..5934ddc94aa0 100644
--- a/tools/testing/selftests/kvm/x86_64/smaller_maxphyaddr_emulation_test.c
+++ b/tools/testing/selftests/kvm/x86_64/smaller_maxphyaddr_emulation_test.c
@@ -21,9 +21,22 @@ 
 #define MEM_REGION_SLOT	10
 #define MEM_REGION_SIZE PAGE_SIZE
 
-static void guest_code(void)
+static void guest_code(bool tdp_enabled)
 {
-	flds(MEM_REGION_GVA);
+	uint64_t error_code;
+	uint64_t vector;
+
+	vector = kvm_asm_safe_ec(FLDS_MEM_EAX, error_code, "a"(MEM_REGION_GVA));
+
+	/*
+	 * When TDP is disabled, no instruction emulation is required so flds
+	 * should generate #PF(RSVD).
+	 */
+	if (!tdp_enabled) {
+		GUEST_ASSERT_EQ(vector, PF_VECTOR);
+		GUEST_ASSERT(error_code & PFERR_RSVD_MASK);
+	}
+
 	GUEST_DONE();
 }
 
@@ -32,6 +45,7 @@  int main(int argc, char *argv[])
 	struct kvm_vcpu *vcpu;
 	struct kvm_vm *vm;
 	uint64_t gpa, pte;
+	struct ucall uc;
 	uint64_t *hva;
 	int rc;
 
@@ -41,6 +55,10 @@  int main(int argc, char *argv[])
 	TEST_REQUIRE(kvm_has_cap(KVM_CAP_SMALLER_MAXPHYADDR));
 
 	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+	vcpu_args_set(vcpu, 1, kvm_is_tdp_enabled());
+
+	vm_init_descriptor_tables(vm);
+	vcpu_init_descriptor_tables(vcpu);
 
 	vcpu_set_cpuid_maxphyaddr(vcpu, MAXPHYADDR);
 
@@ -61,10 +79,27 @@  int main(int argc, char *argv[])
 	vm_set_page_table_entry(vm, vcpu, MEM_REGION_GVA, pte | (1ull << 36));
 
 	vcpu_run(vcpu);
-	assert_exit_for_flds_emulation_failure(vcpu);
-	skip_flds_instruction(vcpu);
-	vcpu_run(vcpu);
-	ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);
+
+	/*
+	 * When TDP is enabled, KVM must emulate the flds instruction, which
+	 * results in an emulation failure out to userspace since KVM does not
+	 * know how to emulate flds.
+	 */
+	if (kvm_is_tdp_enabled()) {
+		assert_exit_for_flds_emulation_failure(vcpu);
+		skip_flds_instruction(vcpu);
+		vcpu_run(vcpu);
+	}
+
+	switch (get_ucall(vcpu, &uc)) {
+	case UCALL_ABORT:
+		REPORT_GUEST_ASSERT(uc);
+		break;
+	case UCALL_DONE:
+		break;
+	default:
+		TEST_FAIL("Unrecognized ucall: %lu\n", uc.cmd);
+	}
 
 	kvm_vm_free(vm);