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 process to validate
the CPUID entries reported by KVM_GET_CPUID2 prior to initial guest
start.
[1]: SEV SNP Firmware ABI Specification, Rev. 0.8, 8.13.2.6
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
target/i386/sev.c | 146 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 143 insertions(+), 3 deletions(-)
diff --git a/target/i386/sev.c b/target/i386/sev.c
index 0009c93d28..72a6146295 100644
--- a/target/i386/sev.c
+++ b/target/i386/sev.c
@@ -153,6 +153,36 @@ 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)
{
@@ -1141,6 +1171,117 @@ detect_first_overlap(uint64_t start, uint64_t end, Range *range_list,
return overlap;
}
+static int
+sev_snp_cpuid_info_fill(SnpCpuidInfo *snp_cpuid_info,
+ const KvmCpuidInfo *kvm_cpuid_info)
+{
+ size_t i;
+
+ memset(snp_cpuid_info, 0, sizeof(*snp_cpuid_info));
+
+ for (i = 0; kvm_cpuid_info->entries[i].function != 0xFFFFFFFF; 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;
+
+ if (snp_cpuid_entry->eax_in == 0xD &&
+ (snp_cpuid_entry->ecx_in == 0x0 || snp_cpuid_entry->ecx_in == 0x1)) {
+ snp_cpuid_entry->ebx = 0x240;
+ }
+ }
+
+ if (i > SNP_CPUID_FUNCTION_MAXCOUNT) {
+ error_report("SEV-SNP: CPUID count '%lu' exceeds max '%u'",
+ i, SNP_CPUID_FUNCTION_MAXCOUNT);
+ return -1;
+ }
+
+ snp_cpuid_info->count = i;
+
+ return 0;
+}
+
+static void
+sev_snp_cpuid_report_mismatches(SnpCpuidInfo *old,
+ SnpCpuidInfo *new)
+{
+ size_t i;
+
+ 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 %x, index: %x.\n"
+ "provided: eax:0x%08x, ebx: 0x%08x, ecx: 0x%08x, edx: 0x%08x\n"
+ "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 int
+sev_snp_launch_update_cpuid(uint32_t cpuid_addr, uint32_t cpuid_len)
+{
+ KvmCpuidInfo kvm_cpuid_info;
+ SnpCpuidInfo snp_cpuid_info;
+ CPUState *cs = first_cpu;
+ MemoryRegion *mr = NULL;
+ void *snp_cpuid_hva;
+ int ret;
+
+ snp_cpuid_hva = gpa2hva(&mr, cpuid_addr, cpuid_len, NULL);
+ if (!snp_cpuid_hva) {
+ error_report("SEV-SNP: unable to access CPUID memory range at GPA %d",
+ cpuid_addr);
+ return 1;
+ }
+
+ /* get the cpuid list from KVM */
+ memset(&kvm_cpuid_info.entries, 0xFF,
+ KVM_MAX_CPUID_ENTRIES * sizeof(struct kvm_cpuid_entry2));
+ kvm_cpuid_info.cpuid.nent = KVM_MAX_CPUID_ENTRIES;
+
+ ret = kvm_vcpu_ioctl(cs, KVM_GET_CPUID2, &kvm_cpuid_info);
+ if (ret) {
+ error_report("SEV-SNP: unable to query CPUID values for CPU: '%s'",
+ strerror(-ret));
+ }
+
+ ret = sev_snp_cpuid_info_fill(&snp_cpuid_info, &kvm_cpuid_info);
+ if (ret) {
+ error_report("SEV-SNP: failed to generate CPUID table information");
+ exit(1);
+ }
+
+ memcpy(snp_cpuid_hva, &snp_cpuid_info, sizeof(snp_cpuid_info));
+
+ ret = sev_snp_launch_update_gpa(cpuid_addr, cpuid_len,
+ KVM_SEV_SNP_PAGE_TYPE_CPUID);
+ if (ret) {
+ sev_snp_cpuid_report_mismatches(&snp_cpuid_info, snp_cpuid_hva);
+ error_report("SEV-SNP: failed update CPUID page");
+ exit(1);
+ }
+
+ return 0;
+}
+
static void snp_ovmf_boot_block_setup(void)
{
SevSnpBootInfoBlock *info;
@@ -1176,10 +1317,9 @@ static void snp_ovmf_boot_block_setup(void)
}
/* Populate the cpuid page */
- ret = sev_snp_launch_update_gpa(info->cpuid_addr, info->cpuid_len,
- KVM_SEV_SNP_PAGE_TYPE_CPUID);
+ ret = sev_snp_launch_update_cpuid(info->cpuid_addr, info->cpuid_len);
if (ret) {
- error_report("SEV-SNP: failed to insert cpuid page GPA 0x%x",
+ error_report("SEV-SNP: failed to populate cpuid tables GPA 0x%x",
info->cpuid_addr);
exit(1);
}
--
2.25.1
