diff mbox series

[v8,10/10] KVM: selftests: Add a basic SEV smoke test

Message ID 20240203000917.376631-11-seanjc@google.com (mailing list archive)
State New, archived
Headers show
Series KVM: selftests: Add SEV smoke test | expand

Commit Message

Sean Christopherson Feb. 3, 2024, 12:09 a.m. UTC 
From: Peter Gonda <pgonda@google.com>

Add a basic smoke test for SEV guests to verify that KVM can launch an
SEV guest and run a few instructions without exploding.  To verify that
SEV is indeed enabled, assert that SEV is reported as enabled in
MSR_AMD64_SEV, a.k.a. SEV_STATUS, which cannot be intercepted by KVM
(architecturally enforced).

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vishal Annapurve <vannapurve@google.com>
Cc: Ackerly Tng <ackerleytng@google.com>
cc: Andrew Jones <andrew.jones@linux.dev>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Suggested-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Peter Gonda <pgonda@google.com>
[sean: rename to "sev_smoke_test"]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 tools/testing/selftests/kvm/Makefile          |  1 +
 .../selftests/kvm/x86_64/sev_smoke_test.c     | 58 +++++++++++++++++++
 2 files changed, 59 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/x86_64/sev_smoke_test.c

Comments

Sean Christopherson Feb. 6, 2024, 8:36 p.m. UTC | #1 
On Fri, Feb 02, 2024, Sean Christopherson wrote:
> +int main(int argc, char *argv[])
> +{
> +	TEST_REQUIRE(is_kvm_sev_supported());

This also needs

	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SEV));

to handle the case where the platform supports SEV, i.e. /dev/sev exists, but
KVM doesn't support SEV, e.g. if TDP is disabled, if SEV was explicitly disabled
via module param, etc.
Sean Christopherson Feb. 22, 2024, 10:42 p.m. UTC | #2 
On Tue, Feb 06, 2024, Sean Christopherson wrote:
> On Fri, Feb 02, 2024, Sean Christopherson wrote:
> > +int main(int argc, char *argv[])
> > +{
> > +	TEST_REQUIRE(is_kvm_sev_supported());
> 
> This also needs
> 
> 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SEV));
> 
> to handle the case where the platform supports SEV, i.e. /dev/sev exists, but
> KVM doesn't support SEV, e.g. if TDP is disabled, if SEV was explicitly disabled
> via module param, etc.

Thinking more about this, I think we should simply delete is_kvm_sev_supported().
(a) it obviously doesn't query _KVM_ support, and (b) if KVM says SEV is supported,
then it darn well actually be supported.
Sean Christopherson Feb. 22, 2024, 10:55 p.m. UTC | #3 
On Thu, Feb 22, 2024, Sean Christopherson wrote:
> On Tue, Feb 06, 2024, Sean Christopherson wrote:
> > On Fri, Feb 02, 2024, Sean Christopherson wrote:
> > > +int main(int argc, char *argv[])
> > > +{
> > > +	TEST_REQUIRE(is_kvm_sev_supported());
> > 
> > This also needs
> > 
> > 	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SEV));
> > 
> > to handle the case where the platform supports SEV, i.e. /dev/sev exists, but
> > KVM doesn't support SEV, e.g. if TDP is disabled, if SEV was explicitly disabled
> > via module param, etc.
> 
> Thinking more about this, I think we should simply delete is_kvm_sev_supported().
> (a) it obviously doesn't query _KVM_ support, and (b) if KVM says SEV is supported,
> then it darn well actually be supported.

Ugh, and selftests also need to handle the scenario where SEV is enabled, but all
ASIDs are assigned to SEV-ES.  We could try to create a dummy VM and check for an
-EBUSY return, but that is ugly and could result in missing KVM bugs due to tests
being skipped instead of failing.

That's a future problem though, because I think we'll need new KVM functionality
to surface that information.
diff mbox series

Patch

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 169b6ee8f733..da20e6bb43ed 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -120,6 +120,7 @@  TEST_GEN_PROGS_x86_64 += x86_64/vmx_pmu_caps_test
 TEST_GEN_PROGS_x86_64 += x86_64/xen_shinfo_test
 TEST_GEN_PROGS_x86_64 += x86_64/xen_vmcall_test
 TEST_GEN_PROGS_x86_64 += x86_64/sev_migrate_tests
+TEST_GEN_PROGS_x86_64 += x86_64/sev_smoke_test
 TEST_GEN_PROGS_x86_64 += x86_64/amx_test
 TEST_GEN_PROGS_x86_64 += x86_64/max_vcpuid_cap_test
 TEST_GEN_PROGS_x86_64 += x86_64/triple_fault_event_test
diff --git a/tools/testing/selftests/kvm/x86_64/sev_smoke_test.c b/tools/testing/selftests/kvm/x86_64/sev_smoke_test.c
new file mode 100644
index 000000000000..c1534efab2be
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/sev_smoke_test.c
@@ -0,0 +1,58 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "svm_util.h"
+#include "linux/psp-sev.h"
+#include "sev.h"
+
+static void guest_sev_code(void)
+{
+	GUEST_ASSERT(this_cpu_has(X86_FEATURE_SEV));
+	GUEST_ASSERT(rdmsr(MSR_AMD64_SEV) & MSR_AMD64_SEV_ENABLED);
+
+	GUEST_DONE();
+}
+
+static void test_sev(void *guest_code, uint64_t policy)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+	struct ucall uc;
+
+	vm = vm_sev_create_with_one_vcpu(policy, guest_code, &vcpu);
+
+	for (;;) {
+		vcpu_run(vcpu);
+
+		switch (get_ucall(vcpu, &uc)) {
+		case UCALL_SYNC:
+			continue;
+		case UCALL_DONE:
+			return;
+		case UCALL_ABORT:
+			REPORT_GUEST_ASSERT(uc);
+		default:
+			TEST_FAIL("Unexpected exit: %s",
+				  exit_reason_str(vcpu->run->exit_reason));
+		}
+	}
+
+	kvm_vm_free(vm);
+}
+
+int main(int argc, char *argv[])
+{
+	TEST_REQUIRE(is_kvm_sev_supported());
+
+	test_sev(guest_sev_code, SEV_POLICY_NO_DBG);
+	test_sev(guest_sev_code, 0);
+
+	return 0;
+}