bool cpu_has_ibpb_brtype_microcode(void)
{
- u8 fam = boot_cpu_data.x86;
-
+ switch (boot_cpu_data.x86) {
/* Zen1/2 IBPB flushes branch type predictions too. */
- if (fam == 0x17)
+ case 0x17:
return boot_cpu_has(X86_FEATURE_AMD_IBPB);
- /* Poke the MSR bit on Zen3/4 to check its presence. */
- else if (fam == 0x19)
- return !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB);
- else
+ case 0x19:
+ /* Poke the MSR bit on Zen3/4 to check its presence. */
+ if (!wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
+ setup_force_cpu_cap(X86_FEATURE_SBPB);
+ return true;
+ } else {
+ return false;
+ }
+ default:
return false;
+ }
}
static void zenbleed_check_cpu(void *unused)
* flags for guests.
*/
setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
- setup_force_cpu_cap(X86_FEATURE_SBPB);
/*
* Zen1/2 with SMT off aren't vulnerable after the right
* IBPB microcode has been applied.
*/
if ((boot_cpu_data.x86 < 0x19) &&
- (cpu_smt_control == CPU_SMT_DISABLED))
+ (!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED)))
setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
}
pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
pred_cmd:
- if (boot_cpu_has(X86_FEATURE_SRSO_NO) ||
- srso_cmd == SRSO_CMD_OFF)
+ if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) &&
+ boot_cpu_has(X86_FEATURE_SBPB))
x86_pred_cmd = PRED_CMD_SBPB;
}