[tip: x86/urgent] x86/srso: Fix srso_show_state() side effect
From: tip-bot2 for Josh Poimboeuf
Date: Tue Sep 19 2023 - 05:45:29 EST
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: a8cf700c17d9ca6cb8ee7dc5c9330dbac3948237
Gitweb: https://git.kernel.org/tip/a8cf700c17d9ca6cb8ee7dc5c9330dbac3948237
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Mon, 04 Sep 2023 22:04:45 -07:00
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 19 Sep 2023 10:53:34 +02:00
x86/srso: Fix srso_show_state() side effect
Reading the 'spec_rstack_overflow' sysfs file can trigger an unnecessary
MSR write, and possibly even a (handled) exception if the microcode
hasn't been updated.
Avoid all that by just checking X86_FEATURE_IBPB_BRTYPE instead, which
gets set by srso_select_mitigation() if the updated microcode exists.
Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Acked-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/r/27d128899cb8aee9eb2b57ddc996742b0c1d776b.1693889988.git.jpoimboe@xxxxxxxxxx
---
arch/x86/kernel/cpu/bugs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f081d26..bdd3e29 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2717,7 +2717,7 @@ static ssize_t srso_show_state(char *buf)
return sysfs_emit(buf, "%s%s\n",
srso_strings[srso_mitigation],
- (cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));
+ boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
}
static ssize_t gds_show_state(char *buf)