From: "Borislav Petkov (AMD)" <bp@alien8.de>
Date: Sun, 13 Aug 2023 12:39:34 +0200
Subject: x86/srso: Disable the mitigation on unaffected configurations
Git-commit: e9fbc47b818b964ddff5df5b2d5c0f5f32f4a147
Patch-mainline: v6.5-rc7
References: git-fixes
Skip the srso cmd line parsing which is not needed on Zen1/2 with SMT
disabled and with the proper microcode applied (latter should be the
case anyway) as those are not affected.
Fixes: 5a15d8348881 ("x86/srso: Tie SBPB bit setting to microcode patch detection")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230813104517.3346-1-bp@alien8.de
Acked-by: nborisov <nik.borisov@suse.com>
---
arch/x86/kernel/cpu/bugs.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d02f73c5339d..6c04aef4b63b 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2418,8 +2418,10 @@ static void __init srso_select_mitigation(void)
* IBPB microcode has been applied.
*/
if ((boot_cpu_data.x86 < 0x19) &&
- (!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED)))
+ (!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED))) {
setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
+ return;
+ }
}
if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
@@ -2696,6 +2698,9 @@ static ssize_t retbleed_show_state(char *buf)
static ssize_t srso_show_state(char *buf)
{
+ if (boot_cpu_has(X86_FEATURE_SRSO_NO))
+ return sysfs_emit(buf, "Not affected\n");
+
return sysfs_emit(buf, "%s%s\n",
srso_strings[srso_mitigation],
(cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));