[PATCH v6 2/4] x86/tests: Add tests for AMD SEV-ES #VC handling Add KUnit based tests to validate Linux's VC handling for instructions cpuid and wbinvd. These tests: 1. install a kretprobe on the #VC handler (sev_es_ghcb_hv_call, to access GHCB before/after the resulting VMGEXIT). 2. trigger an NAE by executing either cpuid or wbinvd. 3. check that the kretprobe was hit with the right exit_code available in GHCB.

Vasant Karasulli
2022-03-18T09:45:44Z

Signed-off-by: Vasant Karasulli <vkarasulli@suse.de>
---
arch/x86/tests/Makefile | 2 +
arch/x86/tests/sev-test-vc.c | 114 +++++++++++++++++++++++++++++++++++
2 files changed, 116 insertions(+)
create mode 100644 arch/x86/tests/sev-test-vc.c

diff --git a/arch/x86/tests/Makefile b/arch/x86/tests/Makefile
index f66554cd5c45..4beca64bd2aa 100644
--- a/arch/x86/tests/Makefile
+++ b/arch/x86/tests/Makefile
@@ -1 +1,3 @@
# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_AMD_SEV_TEST_VC) += sev-test-vc.o
diff --git a/arch/x86/tests/sev-test-vc.c b/arch/x86/tests/sev-test-vc.c
new file mode 100644
index 000000000000..9d415b9708dc
--- /dev/null
+++ b/arch/x86/tests/sev-test-vc.c
@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 SUSE
+ *
+ * Author: Varad Gautam <varad.gautam@suse.com>
+ */
+
+#include <asm/cpufeature.h>
+#include <asm/sev-common.h>
+#include <asm/svm.h>
+#include <kunit/test.h>
+#include <linux/kprobes.h>
+
+static struct kretprobe hv_call_krp;
+
+static int hv_call_krp_entry(struct kretprobe_instance *krpi,
+ struct pt_regs *regs)
+{
+ unsigned long ghcb_vaddr = regs_get_kernel_argument(regs, 0);
+ *((unsigned long *) krpi->data) = ghcb_vaddr;
+
+ return 0;
+}
+
+static int hv_call_krp_ret(struct kretprobe_instance *krpi,
+ struct pt_regs *regs)
+{
+ unsigned long ghcb_vaddr = *((unsigned long *) krpi->data);
+ struct ghcb *ghcb = (struct ghcb *) ghcb_vaddr;
+ struct kunit *test = current->kunit_test;
+
+ if (test && strstr(test->name, "sev_es_") && test->priv)
+ *((u64 *)test->priv) = ghcb->save.sw_exit_code;
+
+ return 0;
+}
+
+int sev_es_test_vc_init(struct kunit *test)
+{
+ int ret;
+
+ if (!cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT)) {
+ kunit_info(test, "Not a SEV-ES guest. Skipping.");
+ ret = -EINVAL;
+ goto out;
+ }
+
+ memset(&hv_call_krp, 0, sizeof(hv_call_krp));
+ hv_call_krp.entry_handler = hv_call_krp_entry;
+ hv_call_krp.handler = hv_call_krp_ret;
+ hv_call_krp.maxactive = 100;
+ hv_call_krp.data_size = sizeof(unsigned long);
+ hv_call_krp.kp.symbol_name = "sev_es_ghcb_hv_call";
+ hv_call_krp.kp.addr = 0;
+
+ ret = register_kretprobe(&hv_call_krp);
+ if (ret) {
+ kunit_info(test, "Could not register kretprobe. Skipping.");
+ goto out;
+ }
+
+ test->priv = kunit_kzalloc(test, sizeof(u64), GFP_KERNEL);
+ if (!test->priv) {
+ ret = -ENOMEM;
+ kunit_info(test, "Could not allocate. Skipping.");
+ goto out;
+ }
+
+out:
+ return ret;
+}
+
+void sev_es_test_vc_exit(struct kunit *test)
+{
+ if (test->priv)
+ kunit_kfree(test, test->priv);
+
+ if (hv_call_krp.kp.addr)
+ unregister_kretprobe(&hv_call_krp);
+}
+
+#define check_op(kt, ec, op) \
+do { \
+ struct kunit *t = (struct kunit *) kt; \
+ op; \
+ KUNIT_EXPECT_EQ(t, (typeof(ec)) ec, \
+ *((typeof(ec) *)(t->priv))); \
+} while (0)
+
+static void sev_es_nae_cpuid(struct kunit *test)
+{
+ unsigned int cpuid_fn = 0x8000001f;
+
+ check_op(test, SVM_EXIT_CPUID, native_cpuid_eax(cpuid_fn));
+}
+
+static void sev_es_nae_wbinvd(struct kunit *test)
+{
+ check_op(test, SVM_EXIT_WBINVD, wbinvd());
+}
+
+static struct kunit_case sev_es_vc_testcases[] = {
+ KUNIT_CASE(sev_es_nae_cpuid),
+ KUNIT_CASE(sev_es_nae_wbinvd),
+ {}
+};
+
+static struct kunit_suite sev_es_vc_test_suite = {
+ .name = "sev_es_test_vc",
+ .init = sev_es_test_vc_init,
+ .exit = sev_es_test_vc_exit,
+ .test_cases = sev_es_vc_testcases,
+};
+kunit_test_suite(sev_es_vc_test_suite);
--
2.32.0