[PATCH v2] x86: Add a test for AMD SEV-ES #VC handling
From: Varad Gautam
Date: Mon May 31 2021 - 13:27:55 EST
Some vmexits on a SEV-ES guest need special handling within the guest
before exiting to the hypervisor. This must happen within the guest's
\#VC exception handler, triggered on every non automatic exit.
Add a KUnit based test to validate Linux's VC handling. The test:
1. installs a kretprobe on the #VC handler (sev_es_ghcb_hv_call, to
access GHCB before/after the resulting VMGEXIT).
2. tiggers 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@xxxxxxxx>
---
v2: Add a testcase for MMIO read/write.
arch/x86/Kconfig | 9 ++
arch/x86/kernel/Makefile | 5 ++
arch/x86/kernel/sev-test-vc.c | 155 ++++++++++++++++++++++++++++++++++
3 files changed, 169 insertions(+)
create mode 100644 arch/x86/kernel/sev-test-vc.c
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0045e1b441902..0a3c3f31813f1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1543,6 +1543,15 @@ config AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT
If set to N, then the encryption of system memory can be
activated with the mem_encrypt=on command line option.
+config AMD_MEM_ENCRYPT_TEST_VC
+ bool "Test for AMD Secure Memory Encryption (SME) support"
+ depends on AMD_MEM_ENCRYPT
+ select KUNIT
+ select FUNCTION_TRACER
+ help
+ Enable KUnit-based testing for the encryption of system memory
+ using AMD SEV-ES. Currently only tests #VC handling.
+
# Common NUMA Features
config NUMA
bool "NUMA Memory Allocation and Scheduler Support"
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 0f66682ac02a6..360c5d33580ca 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -23,6 +23,10 @@ CFLAGS_REMOVE_head64.o = -pg
CFLAGS_REMOVE_sev.o = -pg
endif
+ifdef CONFIG_AMD_MEM_ENCRYPT_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
@@ -149,6 +153,7 @@ obj-$(CONFIG_UNWINDER_FRAME_POINTER) += unwind_frame.o
obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o
obj-$(CONFIG_AMD_MEM_ENCRYPT) += sev.o
+obj-$(CONFIG_AMD_MEM_ENCRYPT_TEST_VC) += sev-test-vc.o
###
# 64 bit specific files
ifeq ($(CONFIG_X86_64),y)
diff --git a/arch/x86/kernel/sev-test-vc.c b/arch/x86/kernel/sev-test-vc.c
new file mode 100644
index 0000000000000..2475270b844e8
--- /dev/null
+++ b/arch/x86/kernel/sev-test-vc.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 SUSE
+ *
+ * Author: Varad Gautam <varad.gautam@xxxxxxxx>
+ */
+
+#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)
+ cmpxchg((unsigned long *) test->priv, ghcb->save.sw_exit_code, 1);
+
+ return 0;
+}
+
+int sev_test_vc_init(struct kunit *test)
+{
+ int ret;
+
+ if (!sev_es_active()) {
+ pr_err("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 < 0) {
+ pr_err("Could not register kretprobe. Skipping.");
+ goto out;
+ }
+
+ test->priv = kunit_kzalloc(test, sizeof(unsigned long), GFP_KERNEL);
+ if (!test->priv) {
+ ret = -ENOMEM;
+ pr_err("Could not allocate. Skipping.");
+ goto out;
+ }
+
+out:
+ return ret;
+}
+
+void sev_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 guarded_op(kt, ec, op) \
+do { \
+ struct kunit *t = (struct kunit *) kt; \
+ smp_store_release((typeof(ec) *) t->priv, ec); \
+ op; \
+ KUNIT_EXPECT_EQ(t, (typeof(ec)) 1, \
+ (typeof(ec)) smp_load_acquire((typeof(ec) *) t->priv)); \
+} while(0)
+
+static void sev_es_nae_cpuid(struct kunit *test)
+{
+ unsigned int cpuid_fn = 0x8000001f;
+
+ guarded_op(test, SVM_EXIT_CPUID, native_cpuid_eax(cpuid_fn));
+}
+
+static void sev_es_nae_wbinvd(struct kunit *test)
+{
+ guarded_op(test, SVM_EXIT_WBINVD, wbinvd());
+}
+
+static void sev_es_nae_msr(struct kunit *test)
+{
+ guarded_op(test, SVM_EXIT_MSR, __rdmsr(MSR_IA32_TSC));
+}
+
+static void sev_es_nae_dr7_rw(struct kunit *test)
+{
+ guarded_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;
+
+ guarded_op(test, SVM_EXIT_IOIO, val = inb(port));
+ guarded_op(test, SVM_EXIT_IOIO, outb(val, port));
+ guarded_op(test, SVM_EXIT_IOIO, insb(port, &val, sizeof(val)));
+ guarded_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 __iomem *lapic = ioremap(lapic_ver_pa, 0x4);
+ unsigned lapic_version = 0;
+
+ guarded_op(test, SVM_VMGEXIT_MMIO_READ, lapic_version = *lapic);
+ guarded_op(test, SVM_VMGEXIT_MMIO_WRITE, *lapic = lapic_version);
+
+ iounmap(lapic);
+}
+
+static struct kunit_case sev_test_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_vc_test_suite = {
+ .name = "sev_test_vc",
+ .init = sev_test_vc_init,
+ .exit = sev_test_vc_exit,
+ .test_cases = sev_test_vc_testcases,
+};
+kunit_test_suite(sev_vc_test_suite);
--
2.30.2