From: Michael Roth <michael.roth@amd.com>
SEV-SNP firmware allows a special guest page to be populated with a
table of guest CPUID values so that they can be validated through
firmware before being loaded into encrypted guest memory where they can
be used in place of hypervisor-provided values[1].
As part of SEV-SNP guest initialization, use this interface to validate
the CPUID entries reported by KVM_GET_CPUID2 prior to initial guest
start and populate the CPUID page reserved by OVMF with the resulting
encrypted data.
[1] SEV SNP Firmware ABI Specification, Rev. 0.8, 8.13.2.6
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Pankaj Gupta <pankaj.gupta@amd.com>
Message-ID: <20240530111643.1091816-21-pankaj.gupta@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
target/i386/sev.c | 164 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 162 insertions(+), 2 deletions(-)
diff --git a/target/i386/sev.c b/target/i386/sev.c
index c57534fca2b..06401f0526f 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -200,6 +200,36 @@ static const char *const sev_fw_errlist[] = {
#define SEV_FW_MAX_ERROR ARRAY_SIZE(sev_fw_errlist)
+/* <linux/kvm.h> doesn't expose this, so re-use the max from kvm.c */
+#define KVM_MAX_CPUID_ENTRIES 100
+
+typedef struct KvmCpuidInfo {
+ struct kvm_cpuid2 cpuid;
+ struct kvm_cpuid_entry2 entries[KVM_MAX_CPUID_ENTRIES];
+} KvmCpuidInfo;
+
+#define SNP_CPUID_FUNCTION_MAXCOUNT 64
+#define SNP_CPUID_FUNCTION_UNKNOWN 0xFFFFFFFF
+
+typedef struct {
+ uint32_t eax_in;
+ uint32_t ecx_in;
+ uint64_t xcr0_in;
+ uint64_t xss_in;
+ uint32_t eax;
+ uint32_t ebx;
+ uint32_t ecx;
+ uint32_t edx;
+ uint64_t reserved;
+} __attribute__((packed)) SnpCpuidFunc;
+
+typedef struct {
+ uint32_t count;
+ uint32_t reserved1;
+ uint64_t reserved2;
+ SnpCpuidFunc entries[SNP_CPUID_FUNCTION_MAXCOUNT];
+} __attribute__((packed)) SnpCpuidInfo;
+
static int
sev_ioctl(int fd, int cmd, void *data, int *error)
{
@@ -788,6 +818,35 @@ out:
return ret;
}
+static void
+sev_snp_cpuid_report_mismatches(SnpCpuidInfo *old,
+ SnpCpuidInfo *new)
+{
+ size_t i;
+
+ if (old->count != new->count) {
+ error_report("SEV-SNP: CPUID validation failed due to count mismatch,"
+ "provided: %d, expected: %d", old->count, new->count);
+ return;
+ }
+
+ for (i = 0; i < old->count; i++) {
+ SnpCpuidFunc *old_func, *new_func;
+
+ old_func = &old->entries[i];
+ new_func = &new->entries[i];
+
+ if (memcmp(old_func, new_func, sizeof(SnpCpuidFunc))) {
+ error_report("SEV-SNP: CPUID validation failed for function 0x%x, index: 0x%x"
+ "provided: eax:0x%08x, ebx: 0x%08x, ecx: 0x%08x, edx: 0x%08x"
+ "expected: eax:0x%08x, ebx: 0x%08x, ecx: 0x%08x, edx: 0x%08x",
+ old_func->eax_in, old_func->ecx_in,
+ old_func->eax, old_func->ebx, old_func->ecx, old_func->edx,
+ new_func->eax, new_func->ebx, new_func->ecx, new_func->edx);
+ }
+ }
+}
+
static const char *
snp_page_type_to_str(int type)
{
@@ -806,6 +865,7 @@ sev_snp_launch_update(SevSnpGuestState *sev_snp_guest,
SevLaunchUpdateData *data)
{
int ret, fw_error;
+ SnpCpuidInfo snp_cpuid_info;
struct kvm_sev_snp_launch_update update = {0};
if (!data->hva || !data->len) {
@@ -815,6 +875,11 @@ sev_snp_launch_update(SevSnpGuestState *sev_snp_guest,
return 1;
}
+ if (data->type == KVM_SEV_SNP_PAGE_TYPE_CPUID) {
+ /* Save a copy for comparison in case the LAUNCH_UPDATE fails */
+ memcpy(&snp_cpuid_info, data->hva, sizeof(snp_cpuid_info));
+ }
+
update.uaddr = (__u64)(unsigned long)data->hva;
update.gfn_start = data->gpa >> TARGET_PAGE_BITS;
update.len = data->len;
@@ -842,6 +907,11 @@ sev_snp_launch_update(SevSnpGuestState *sev_snp_guest,
if (ret && ret != -EAGAIN) {
error_report("SNP_LAUNCH_UPDATE ret=%d fw_error=%d '%s'",
ret, fw_error, fw_error_to_str(fw_error));
+
+ if (data->type == KVM_SEV_SNP_PAGE_TYPE_CPUID) {
+ sev_snp_cpuid_report_mismatches(&snp_cpuid_info, data->hva);
+ error_report("SEV-SNP: failed update CPUID page");
+ }
break;
}
}
@@ -1004,7 +1074,8 @@ sev_launch_finish(SevCommonState *sev_common)
}
static int
-snp_launch_update_data(uint64_t gpa, void *hva, uint32_t len, int type)
+snp_launch_update_data(uint64_t gpa, void *hva,
+ uint32_t len, int type)
{
SevLaunchUpdateData *data;
@@ -1019,6 +1090,90 @@ snp_launch_update_data(uint64_t gpa, void *hva, uint32_t len, int type)
return 0;
}
+static int
+sev_snp_cpuid_info_fill(SnpCpuidInfo *snp_cpuid_info,
+ const KvmCpuidInfo *kvm_cpuid_info)
+{
+ size_t i;
+
+ if (kvm_cpuid_info->cpuid.nent > SNP_CPUID_FUNCTION_MAXCOUNT) {
+ error_report("SEV-SNP: CPUID entry count (%d) exceeds max (%d)",
+ kvm_cpuid_info->cpuid.nent, SNP_CPUID_FUNCTION_MAXCOUNT);
+ return -1;
+ }
+
+ memset(snp_cpuid_info, 0, sizeof(*snp_cpuid_info));
+
+ for (i = 0; i < kvm_cpuid_info->cpuid.nent; i++) {
+ const struct kvm_cpuid_entry2 *kvm_cpuid_entry;
+ SnpCpuidFunc *snp_cpuid_entry;
+
+ kvm_cpuid_entry = &kvm_cpuid_info->entries[i];
+ snp_cpuid_entry = &snp_cpuid_info->entries[i];
+
+ snp_cpuid_entry->eax_in = kvm_cpuid_entry->function;
+ if (kvm_cpuid_entry->flags == KVM_CPUID_FLAG_SIGNIFCANT_INDEX) {
+ snp_cpuid_entry->ecx_in = kvm_cpuid_entry->index;
+ }
+ snp_cpuid_entry->eax = kvm_cpuid_entry->eax;
+ snp_cpuid_entry->ebx = kvm_cpuid_entry->ebx;
+ snp_cpuid_entry->ecx = kvm_cpuid_entry->ecx;
+ snp_cpuid_entry->edx = kvm_cpuid_entry->edx;
+
+ /*
+ * Guest kernels will calculate EBX themselves using the 0xD
+ * subfunctions corresponding to the individual XSAVE areas, so only
+ * encode the base XSAVE size in the initial leaves, corresponding
+ * to the initial XCR0=1 state.
+ */
+ if (snp_cpuid_entry->eax_in == 0xD &&
+ (snp_cpuid_entry->ecx_in == 0x0 || snp_cpuid_entry->ecx_in == 0x1)) {
+ snp_cpuid_entry->ebx = 0x240;
+ snp_cpuid_entry->xcr0_in = 1;
+ snp_cpuid_entry->xss_in = 0;
+ }
+ }
+
+ snp_cpuid_info->count = i;
+
+ return 0;
+}
+
+static int
+snp_launch_update_cpuid(uint32_t cpuid_addr, void *hva, uint32_t cpuid_len)
+{
+ KvmCpuidInfo kvm_cpuid_info = {0};
+ SnpCpuidInfo snp_cpuid_info;
+ CPUState *cs = first_cpu;
+ int ret;
+ uint32_t i = 0;
+
+ assert(sizeof(snp_cpuid_info) <= cpuid_len);
+
+ /* get the cpuid list from KVM */
+ do {
+ kvm_cpuid_info.cpuid.nent = ++i;
+ ret = kvm_vcpu_ioctl(cs, KVM_GET_CPUID2, &kvm_cpuid_info);
+ } while (ret == -E2BIG);
+
+ if (ret) {
+ error_report("SEV-SNP: unable to query CPUID values for CPU: '%s'",
+ strerror(-ret));
+ return 1;
+ }
+
+ ret = sev_snp_cpuid_info_fill(&snp_cpuid_info, &kvm_cpuid_info);
+ if (ret) {
+ error_report("SEV-SNP: failed to generate CPUID table information");
+ return 1;
+ }
+
+ memcpy(hva, &snp_cpuid_info, sizeof(snp_cpuid_info));
+
+ return snp_launch_update_data(cpuid_addr, hva, cpuid_len,
+ KVM_SEV_SNP_PAGE_TYPE_CPUID);
+}
+
static int
snp_metadata_desc_to_page_type(int desc_type)
{
@@ -1053,7 +1208,12 @@ snp_populate_metadata_pages(SevSnpGuestState *sev_snp,
exit(1);
}
- ret = snp_launch_update_data(desc->base, hva, desc->len, type);
+ if (type == KVM_SEV_SNP_PAGE_TYPE_CPUID) {
+ ret = snp_launch_update_cpuid(desc->base, hva, desc->len);
+ } else {
+ ret = snp_launch_update_data(desc->base, hva, desc->len, type);
+ }
+
if (ret) {
error_report("%s: Failed to add metadata page gpa 0x%x+%x type %d",
__func__, desc->base, desc->len, desc->type);
--
2.45.1