linux-kernel - [PATCH v7 2/4] KVM: SEV-ES: Add tests to validate VC handling for CPUID and WBINVD

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Date:   Mon, 13 Jun 2022 19:04:18 +0200
From:   Vasant Karasulli <vkarasulli@...e.de>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     bp@...en8.de, jroedel@...e.de, thomas.lendacky@....com,
        x86@...nel.org, seanjc@...gle.com,
        Vasant Karasulli <vkarasulli@...e.de>
Subject: [PATCH v7 2/4] KVM: SEV-ES:  Add tests to validate VC handling for 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.

To run these tests, configuration options CONFIG_X86_TESTS and
CONFIG_AMD_SEV_ES_TEST_VC have to be enabled. These tests run
at the kernel boot time. Result of the test execution can be
monitored in the kernel log.

Signed-off-by: Vasant Karasulli <vkarasulli@...e.de>
---
 arch/x86/tests/Makefile      |   3 +
 arch/x86/tests/sev-test-vc.c | 104 +++++++++++++++++++++++++++++++++++
 2 files changed, 107 insertions(+)
 create mode 100644 arch/x86/tests/Makefile
 create mode 100644 arch/x86/tests/sev-test-vc.c

diff --git a/arch/x86/tests/Makefile b/arch/x86/tests/Makefile
new file mode 100644
index 000000000000..4beca64bd2aa
--- /dev/null
+++ b/arch/x86/tests/Makefile
@@ -0,0 +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..900ca357a273
--- /dev/null
+++ b/arch/x86/tests/sev-test-vc.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 SUSE
+ *
+ * Author: Varad Gautam <varad.gautam@...e.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_"))
+		*((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;
+	}
+
+out:
+	return ret;
+}
+
+void sev_es_test_vc_exit(struct kunit *test)
+{
+	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))((u64)(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