x86/CPU/AMD: Make sure EFER[AIBRSE] is set

The AutoIBRS bit gets set only on the BSP as part of determining which
mitigation to enable on AMD. Setting on the APs relies on the
circumstance that the APs get booted through the trampoline and EFER
- the MSR which contains that bit - gets replicated on every AP from the
BSP.

However, this can change in the future and considering the security
implications of this bit not being set on every CPU, make sure it is set
by verifying EFER later in the boot process and on every AP.

Reported-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/r/20230224185257.o3mcmloei5zqu7wa@treble

1 files changed, 1 insertions, 9 deletions

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f9d060e71c3e..182af64387d0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -784,8 +784,7 @@ static int __init nospectre_v1_cmdline(char *str)
 }
 early_param("nospectre_v1", nospectre_v1_cmdline);
 
-static enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init =
-	SPECTRE_V2_NONE;
+enum spectre_v2_mitigation spectre_v2_enabled __ro_after_init = SPECTRE_V2_NONE;
 
 #undef pr_fmt
 #define pr_fmt(fmt)     "RETBleed: " fmt
@@ -1133,13 +1132,6 @@ spectre_v2_parse_user_cmdline(void)
 	return SPECTRE_V2_USER_CMD_AUTO;
 }
 
-static inline bool spectre_v2_in_eibrs_mode(enum spectre_v2_mitigation mode)
-{
-	return mode == SPECTRE_V2_EIBRS ||
-	       mode == SPECTRE_V2_EIBRS_RETPOLINE ||
-	       mode == SPECTRE_V2_EIBRS_LFENCE;
-}
-
 static inline bool spectre_v2_in_ibrs_mode(enum spectre_v2_mitigation mode)
 {
 	return spectre_v2_in_eibrs_mode(mode) || mode == SPECTRE_V2_IBRS;