This is a note to let you know that I've just added the patch titled
x86/srso: Fix srso_show_state() side effect
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-srso-fix-srso_show_state-side-effect.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 29cc9e3da821774dcc2980c380692ec865abb491
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Mon Sep 4 22:04:45 2023 -0700
x86/srso: Fix srso_show_state() side effect
[ Upstream commit a8cf700c17d9ca6cb8ee7dc5c9330dbac3948237 ]
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
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 0d2c5fe841414..78a57737f1ba1 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2692,7 +2692,7 @@ 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 cpu_show_common(struct device *dev, struct device_attribute *attr,
