diff options
| -rw-r--r-- | arch/x86/coco/sev/core.c | 22 | ||||
| -rw-r--r-- | arch/x86/include/asm/sev.h | 17 |
2 files changed, 35 insertions, 4 deletions
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c index b6db4e0b936b..7543a8b52c67 100644 --- a/arch/x86/coco/sev/core.c +++ b/arch/x86/coco/sev/core.c @@ -88,7 +88,7 @@ static const char * const sev_status_feat_names[] = { */ static u64 snp_tsc_scale __ro_after_init; static u64 snp_tsc_offset __ro_after_init; -static u64 snp_tsc_freq_khz __ro_after_init; +static unsigned long snp_tsc_freq_khz __ro_after_init; DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data); DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa); @@ -2167,15 +2167,31 @@ static unsigned long securetsc_get_tsc_khz(void) void __init snp_secure_tsc_init(void) { - unsigned long long tsc_freq_mhz; + struct snp_secrets_page *secrets; + unsigned long tsc_freq_mhz; + void *mem; if (!cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC)) return; + mem = early_memremap_encrypted(sev_secrets_pa, PAGE_SIZE); + if (!mem) { + pr_err("Unable to get TSC_FACTOR: failed to map the SNP secrets page.\n"); + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SECURE_TSC); + } + + secrets = (__force struct snp_secrets_page *)mem; + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); rdmsrq(MSR_AMD64_GUEST_TSC_FREQ, tsc_freq_mhz); - snp_tsc_freq_khz = (unsigned long)(tsc_freq_mhz * 1000); + + /* Extract the GUEST TSC MHZ from BIT[17:0], rest is reserved space */ + tsc_freq_mhz &= GENMASK_ULL(17, 0); + + snp_tsc_freq_khz = SNP_SCALE_TSC_FREQ(tsc_freq_mhz * 1000, secrets->tsc_factor); x86_platform.calibrate_cpu = securetsc_get_tsc_khz; x86_platform.calibrate_tsc = securetsc_get_tsc_khz; + + early_memunmap(mem, PAGE_SIZE); } diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 58e028d42e41..a631f7d7c0c0 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -223,6 +223,18 @@ struct snp_tsc_info_resp { u8 rsvd2[100]; } __packed; +/* + * Obtain the mean TSC frequency by decreasing the nominal TSC frequency with + * TSC_FACTOR as documented in the SNP Firmware ABI specification: + * + * GUEST_TSC_FREQ * (1 - (TSC_FACTOR * 0.00001)) + * + * which is equivalent to: + * + * GUEST_TSC_FREQ -= (GUEST_TSC_FREQ * TSC_FACTOR) / 100000; + */ +#define SNP_SCALE_TSC_FREQ(freq, factor) ((freq) - (freq) * (factor) / 100000) + struct snp_guest_req { void *req_buf; size_t req_sz; @@ -282,8 +294,11 @@ struct snp_secrets_page { u8 svsm_guest_vmpl; u8 rsvd3[3]; + /* The percentage decrease from nominal to mean TSC frequency. */ + u32 tsc_factor; + /* Remainder of page */ - u8 rsvd4[3744]; + u8 rsvd4[3740]; } __packed; struct snp_msg_desc { |