AMD Secure Encrypted Virtualization (SEV) is a hardware accelerated
memory encryption feature that protects guest VMs from host attacks.
This commit provides set up code and a test case for AMD SEV. The set up
code checks if SEV is supported and enabled, and then sets SEV c-bit for
each page table entry.
Signed-off-by: Zixuan Wang <zixuanwang@xxxxxxxxxx>
Co-developed-by: Hyunwook (Wooky) Baek <baekhw@xxxxxxxxxx>
---
configure | 9 +++++++
lib/x86/amd_sev.c | 50 +++++++++++++++++++++++++++++++++++
lib/x86/amd_sev.h | 41 +++++++++++++++++++++++++++++
lib/x86/asm/setup.h | 3 +++
lib/x86/setup.c | 24 +++++++++++++++++
x86/Makefile.common | 10 +++++++
x86/Makefile.x86_64 | 3 +++
x86/amd_sev.c | 64 +++++++++++++++++++++++++++++++++++++++++++++
8 files changed, 204 insertions(+)
create mode 100644 lib/x86/amd_sev.c
create mode 100644 lib/x86/amd_sev.h
create mode 100644 x86/amd_sev.c
diff --git a/configure b/configure
index 3094375..c165ba7 100755
--- a/configure
+++ b/configure
@@ -31,6 +31,8 @@ earlycon=
target_efi=
efi_include_path=
efi_libs_path=
+amd_sev=
+amd_sev_variant=
usage() {
cat <<-EOF
@@ -77,6 +79,7 @@ usage() {
--efi-libs-path Path to GNU-EFI libraries, e.g. "/usr/lib/". This dir should
contain 3 files from GNU-EFI: crt0-efi-x86_64.o, libefi.a,
and libgnuefi.a
+ --amd-sev=VARIANT AMD SEV variant, [SEV|ES|SNP]
EOF
exit 1
}
@@ -150,6 +153,10 @@ while [[ "$1" = -* ]]; do
--efi-libs-path)
efi_libs_path="$arg"
;;
+ --amd-sev)
+ amd_sev=y
+ [ "${arg^^}" != "SEV" ] && amd_sev_variant="${arg^^}"
+ ;;
--help)
usage
;;
@@ -361,6 +368,8 @@ HOST_KEY_DOCUMENT=$host_key_document
TARGET_EFI=$target_efi
EFI_INCLUDE_PATH=$efi_include_path
EFI_LIBS_PATH=$efi_libs_path
+AMD_SEV=$amd_sev
+AMD_SEV_VARIANT=$amd_sev_variant
EOF
if [ "$arch" = "arm" ] || [ "$arch" = "arm64" ]; then
echo "TARGET=$target" >> config.mak
diff --git a/lib/x86/amd_sev.c b/lib/x86/amd_sev.c
new file mode 100644
index 0000000..bd8d536
--- /dev/null
+++ b/lib/x86/amd_sev.c
@@ -0,0 +1,50 @@
+/*
+ * AMD SEV support in KVM-Unit-Tests
+ *
+ * Copyright (c) 2021, Google Inc
+ *
+ * Authors:
+ * Zixuan Wang <zixuanwang@xxxxxxxxxx>
+ *
+ * SPDX-License-Identifier: LGPL-2.0-or-later
+ */
+
+#include "amd_sev.h"
+#include "x86/processor.h"
+
+static unsigned long long amd_sev_c_bit_pos;
+
+EFI_STATUS setup_amd_sev(void)
+{
+ struct cpuid cpuid_out;
+
+ /* Test if we can query SEV features */
+ cpuid_out = cpuid(CPUID_FN_LARGEST_EXT_FUNC_NUM);
+ if (cpuid_out.a < CPUID_FN_ENCRYPT_MEM_CAPAB) {
+ return EFI_UNSUPPORTED;
+ }
+
+ /* Test if SEV is supported */
+ cpuid_out = cpuid(CPUID_FN_ENCRYPT_MEM_CAPAB);
+ if (!(cpuid_out.a & SEV_SUPPORT_MASK)) {
+ return EFI_UNSUPPORTED;
+ }
+
+ /* Test if SEV is enabled */
+ if (!(rdmsr(MSR_SEV_STATUS) & SEV_ENABLED_MASK)) {
+ return EFI_NOT_READY;
+ }
+
+ /* Extract C-Bit position from ebx[5:0]
+ * AMD64 Architecture Programmer's Manual Volume 3
+ * - Section " Function 8000_001Fh - Encrypted Memory Capabilities"
+ */
+ amd_sev_c_bit_pos = (unsigned long long)(cpuid_out.b & 0x3f);
+
+ return EFI_SUCCESS;
+}
+
+unsigned long long get_amd_sev_c_bit_mask(void)
+{
+ return 1ull << amd_sev_c_bit_pos;
+}
diff --git a/lib/x86/amd_sev.h b/lib/x86/amd_sev.h
new file mode 100644
index 0000000..c1b08e8
--- /dev/null
+++ b/lib/x86/amd_sev.h
@@ -0,0 +1,41 @@
+/*
+ * AMD SEV support in KVM-Unit-Tests
+ *
+ * Copyright (c) 2021, Google Inc
+ *
+ * Authors:
+ * Zixuan Wang <zixuanwang@xxxxxxxxxx>
+ *
+ * SPDX-License-Identifier: LGPL-2.0-or-later
+ */
+
+#ifndef _X86_AMD_SEV_H_
+#define _X86_AMD_SEV_H_
+
+#include "libcflat.h"
+#include "desc.h"
+#include "asm/page.h"
+
+#ifdef ALIGN
+#undef ALIGN
+#endif
+#include <efi.h>
+
+/* AMD Programmer's Manual Volume 3
+ * - Section "Function 8000_0000h - Maximum Extended Function Number and Vendor String"
+ * - Section "Function 8000_001Fh - Encrypted Memory Capabilities"
+ */
+#define CPUID_FN_LARGEST_EXT_FUNC_NUM 0x80000000
+#define CPUID_FN_ENCRYPT_MEM_CAPAB 0x8000001f
+#define SEV_SUPPORT_MASK 0b10
+
+/* AMD Programmer's Manual Volume 2
+ * - Section "SEV_STATUS MSR"
+ */
+#define MSR_SEV_STATUS 0xc0010131
+#define SEV_ENABLED_MASK 0b1
+
+EFI_STATUS setup_amd_sev(void);
+unsigned long long get_amd_sev_c_bit_mask(void);
+
+#endif /* _X86_AMD_SEV_H_ */
diff --git a/lib/x86/asm/setup.h b/lib/x86/asm/setup.h
index c32168e..1d69c6e 100644
--- a/lib/x86/asm/setup.h
+++ b/lib/x86/asm/setup.h
@@ -7,6 +7,9 @@
#include "x86/processor.h"
#include "x86/smp.h"
#include "asm/page.h"
+#ifdef CONFIG_AMD_SEV
+#include "x86/amd_sev.h"
+#endif /* CONFIG_AMD_SEV */
#ifdef ALIGN
#undef ALIGN
diff --git a/lib/x86/setup.c b/lib/x86/setup.c
index 0b0dbea..aaa1cce 100644
--- a/lib/x86/setup.c
+++ b/lib/x86/setup.c
@@ -214,6 +214,25 @@ EFI_STATUS setup_efi_pre_boot(UINTN *mapkey, efi_bootinfo_t *efi_bootinfo)
return status;
}
+#ifdef CONFIG_AMD_SEV
+ status = setup_amd_sev();
+ if (EFI_ERROR(status)) {
+ printf("setup_amd_sev() failed: ");
+ switch (status) {
+ case EFI_UNSUPPORTED:
+ printf("SEV is not supported\n");
+ break;
+ case EFI_NOT_READY:
+ printf("SEV is not enabled\n");
+ break;
+ default:
+ printf("Unknown error\n");
+ break;
+ }
+ return status;
+ }
+#endif /* CONFIG_AMD_SEV */
+
return EFI_SUCCESS;
}
@@ -232,6 +251,11 @@ static void setup_page_table(void)
/* Set default flags */
flags = PT_PRESENT_MASK | PT_WRITABLE_MASK | PT_USER_MASK;
+#ifdef CONFIG_AMD_SEV
+ /* Set AMD SEV C-Bit for page table entries */
+ flags |= get_amd_sev_c_bit_mask();
+#endif /* CONFIG_AMD_SEV */
+
/* Level 5 */
curr_pt = (pgd_t *)&ptl5;
curr_pt[0] = ((phys_addr_t)&ptl4) | flags;
diff --git a/x86/Makefile.common b/x86/Makefile.common
index e77de6b..8f9ddad 100644
--- a/x86/Makefile.common
+++ b/x86/Makefile.common
@@ -25,6 +25,9 @@ cflatobjs += lib/x86/delay.o
ifeq ($(TARGET_EFI),y)
cflatobjs += lib/x86/setup.o
cflatobjs += lib/efi.o
+ifeq ($(AMD_SEV),y)
+cflatobjs += lib/x86/amd_sev.o
+endif
endif
OBJDIRS += lib/x86
@@ -38,6 +41,13 @@ COMMON_CFLAGS += -Wa,--divide
endif
COMMON_CFLAGS += -O1
+ifeq ($(AMD_SEV),y)
+COMMON_CFLAGS += -DCONFIG_AMD_SEV
+ifneq ($(AMD_SEV_VARIANT),)
+COMMON_CFLAGS += -DCONFIG_AMD_SEV_$(AMD_SEV_VARIANT)
+endif
+endif
+
# stack.o relies on frame pointers.
KEEP_FRAME_POINTER := y
diff --git a/x86/Makefile.x86_64 b/x86/Makefile.x86_64
index 7e8a57a..c1af80c 100644
--- a/x86/Makefile.x86_64
+++ b/x86/Makefile.x86_64
@@ -32,6 +32,9 @@ tests += $(TEST_DIR)/pks.$(exe)
tests += $(TEST_DIR)/pmu_lbr.$(exe)
tests += $(TEST_DIR)/emulator.$(exe)
tests += $(TEST_DIR)/vmware_backdoors.$(exe)
+ifeq ($(AMD_SEV),y)
+tests += $(TEST_DIR)/amd_sev.$(exe)
+endif
# The following test cases are disabled when building EFI tests because they
# use absolute addresses in their inline assembly code, which cannot compile
diff --git a/x86/amd_sev.c b/x86/amd_sev.c
new file mode 100644
index 0000000..a07a48f
--- /dev/null
+++ b/x86/amd_sev.c
@@ -0,0 +1,64 @@
+/*
+ * AMD SEV test cases
+ *
+ * Copyright (c) 2021, Google Inc
+ *
+ * Authors:
+ * Hyunwook (Wooky) Baek <baekhw@xxxxxxxxxx>
+ * Zixuan Wang <zixuanwang@xxxxxxxxxx>
+ *
+ * SPDX-License-Identifier: LGPL-2.0-or-later
+ */
+
+#include "libcflat.h"
+#include "x86/processor.h"
+#include "x86/amd_sev.h"
+
+#define EXIT_SUCCESS 0
+#define EXIT_FAILURE 1
+
+static int test_sev_activation(void)
+{
+ struct cpuid cpuid_out;
+ u64 msr_out;
+
+ printf("SEV activation test is loaded.\n");
+
+ /* Tests if CPUID function to check SEV is implemented */
+ cpuid_out = cpuid(CPUID_FN_LARGEST_EXT_FUNC_NUM);
+ printf("CPUID Fn8000_0000[EAX]: 0x%08x\n", cpuid_out.a);
+ if (cpuid_out.a < CPUID_FN_ENCRYPT_MEM_CAPAB) {
+ printf("CPUID does not support FN%08x\n",
+ CPUID_FN_ENCRYPT_MEM_CAPAB);
+ return EXIT_FAILURE;
+ }
+
+ /* Tests if SEV is supported */
+ cpuid_out = cpuid(CPUID_FN_ENCRYPT_MEM_CAPAB);
+ printf("CPUID Fn8000_001F[EAX]: 0x%08x\n", cpuid_out.a);
+ printf("CPUID Fn8000_001F[EBX]: 0x%08x\n", cpuid_out.b);
+ if (!(cpuid_out.a & SEV_SUPPORT_MASK)) {
+ printf("SEV is not supported.\n");
+ return EXIT_FAILURE;
+ }
+ printf("SEV is supported\n");
+
+ /* Tests if SEV is enabled */
+ msr_out = rdmsr(MSR_SEV_STATUS);
+ printf("MSR C001_0131[EAX]: 0x%08lx\n", msr_out & 0xffffffff);
+ if (!(msr_out & SEV_ENABLED_MASK)) {
+ printf("SEV is not enabled.\n");
+ return EXIT_FAILURE;
+ }
+ printf("SEV is enabled\n");
+
+ return EXIT_SUCCESS;
+}
+
+int main(void)
+{
+ int rtn;
+ rtn = test_sev_activation();
+ report(rtn == EXIT_SUCCESS, "SEV activation test.");
+ return report_summary();
+}
--
2.33.0.rc1.237.g0d66db33f3-goog
