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i386/sev: Add support for SNP CPUID validation

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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>
This commit is contained in:
Michael Roth 2024-05-30 06:16:32 -05:00 committed by Paolo Bonzini
parent 3d8c2a7f48
commit 70943ad8e4
1 changed files with 162 additions and 2 deletions
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164
target/i386/sev.c
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@ -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);