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x86/srso: Fix srso_show_state() side effect

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[ 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@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/27d128899cb8aee9eb2b57ddc996742b0c1d776b.1693889988.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Josh Poimboeuf 2023-09-04 22:04:45 -07:00 • committed by Greg Kroah-Hartman
parent 7f301aa243
commit 755195b2d2
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kernel/cpu/bugs.c
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@ -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,