Commit a8cf700c authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Borislav Petkov (AMD)
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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: fb3bd914 ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarNikolay Borisov <nik.borisov@suse.com>
Acked-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/27d128899cb8aee9eb2b57ddc996742b0c1d776b.1693889988.git.jpoimboe@kernel.org
parent 10f4c9b9

arch/x86/kernel/cpu/bugs.c

+1 −1
Original line number Diff line number Diff line
@@ -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)