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Date: Tue, 8 Feb 2022 17:26:23 +0100
From: Vasant Karasulli <vkarasulli@...e.de>
To: linux-kernel@...r.kernel.org
Cc: bp@...en8.de, jroedel@...e.de, kvm@...r.kernel.org, x86@...nel.org,
thomas.lendacky@....com, Varad Gautam <varad.gautam@...e.com>,
Vasant Karasulli <vkarasulli@...e.de>
Subject: [PATCH v5 1/1] x86/test: Add a test for AMD SEV-ES #VC handling
From: Varad Gautam <varad.gautam@...e.com>
Add a KUnit based test to validate Linux's VC handling, and introduce
a new CONFIG_X86_TESTS to cover such tests. The test:
1. installs a kretprobe on the #VC handler (sev_es_ghcb_hv_call, to
access GHCB before/after the resulting VMGEXIT).
2. triggers an NAE.
3. checks that the kretprobe was hit with the right exit_code available
in GHCB.
Since relying on kprobes, the test does not cover NMI contexts.
Signed-off-by: Varad Gautam <varad.gautam@...e.com>
Signed-off-by: Vasant Karasulli <vkarasulli@...e.de>
---
arch/x86/Kbuild | 2 +
arch/x86/Kconfig.debug | 16 ++++
arch/x86/kernel/Makefile | 7 ++
arch/x86/tests/Makefile | 3 +
arch/x86/tests/sev-test-vc.c | 154 +++++++++++++++++++++++++++++++++++
5 files changed, 182 insertions(+)
create mode 100644 arch/x86/tests/Makefile
create mode 100644 arch/x86/tests/sev-test-vc.c
diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index f384cb1a4f7a..90470c76866a 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -26,5 +26,7 @@ obj-y += net/
obj-$(CONFIG_KEXEC_FILE) += purgatory/
+obj-y += tests/
+
# for cleaning
subdir- += boot tools
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index d3a6f74a94bd..e4f61af66816 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -279,3 +279,19 @@ endchoice
config FRAME_POINTER
depends on !UNWINDER_ORC && !UNWINDER_GUESS
bool
+
+config X86_TESTS
+ bool "Tests for x86"
+ help
+ This enables building the tests under arch/x86/tests.
+
+if X86_TESTS
+config AMD_SEV_TEST_VC
+ bool "Test for AMD SEV VC exception handling"
+ depends on AMD_MEM_ENCRYPT
+ select FUNCTION_TRACER
+ select KPROBES
+ select KUNIT
+ help
+ Enable KUnit-based testing for AMD SEV #VC exception handling.
+endif # X86_TESTS
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 6aef9ee28a39..69472a576909 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -24,6 +24,13 @@ CFLAGS_REMOVE_sev.o = -pg
CFLAGS_REMOVE_cc_platform.o = -pg
endif
+# AMD_SEV_TEST_VC registers a kprobe by function name. IPA-SRA creates
+# function copies and renames them to have an .isra suffix, which breaks kprobes'
+# lookup. Build with -fno-ipa-sra for the test.
+ifdef CONFIG_AMD_SEV_TEST_VC
+CFLAGS_sev.o += -fno-ipa-sra
+endif
+
KASAN_SANITIZE_head$(BITS).o := n
KASAN_SANITIZE_dumpstack.o := n
KASAN_SANITIZE_dumpstack_$(BITS).o := n
diff --git a/arch/x86/tests/Makefile b/arch/x86/tests/Makefile
new file mode 100644
index 000000000000..4beca64bd2aa
--- /dev/null
+++ b/arch/x86/tests/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(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..eb5f790b64f5
--- /dev/null
+++ b/arch/x86/tests/sev-test-vc.c
@@ -0,0 +1,154 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 SUSE
+ *
+ * Author: Varad Gautam <varad.gautam@...e.com>
+ */
+
+#include <asm/cpufeature.h>
+#include <asm/debugreg.h>
+#include <asm/io.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 void sev_es_nae_msr(struct kunit *test)
+{
+ check_op(test, SVM_EXIT_MSR, __rdmsr(MSR_IA32_TSC));
+}
+
+static void sev_es_nae_dr7_rw(struct kunit *test)
+{
+ check_op(test, SVM_EXIT_WRITE_DR7,
+ native_set_debugreg(7, native_get_debugreg(7)));
+}
+
+static void sev_es_nae_ioio(struct kunit *test)
+{
+ unsigned long port = 0x80;
+ char val = 0;
+
+ check_op(test, SVM_EXIT_IOIO, val = inb(port));
+ check_op(test, SVM_EXIT_IOIO, outb(val, port));
+ check_op(test, SVM_EXIT_IOIO, insb(port, &val, sizeof(val)));
+ check_op(test, SVM_EXIT_IOIO, outsb(port, &val, sizeof(val)));
+}
+
+static void sev_es_nae_mmio(struct kunit *test)
+{
+ unsigned long lapic_ver_pa = 0xfee00030; /* APIC_DEFAULT_PHYS_BASE + APIC_LVR */
+ unsigned long __iomem *lapic = ioremap(lapic_ver_pa, 0x4);
+ unsigned long lapic_version = 0;
+
+ check_op(test, SVM_VMGEXIT_MMIO_READ, lapic_version = *lapic);
+ check_op(test, SVM_VMGEXIT_MMIO_WRITE, *lapic = lapic_version);
+
+ iounmap(lapic);
+}
+
+static struct kunit_case sev_es_vc_testcases[] = {
+ KUNIT_CASE(sev_es_nae_cpuid),
+ KUNIT_CASE(sev_es_nae_wbinvd),
+ KUNIT_CASE(sev_es_nae_msr),
+ KUNIT_CASE(sev_es_nae_dr7_rw),
+ KUNIT_CASE(sev_es_nae_ioio),
+ KUNIT_CASE(sev_es_nae_mmio),
+ {}
+};
+
+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
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