Messages in this thread | | | Date | Mon, 21 Aug 2023 08:04:16 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH 01/22] x86/srso: Fix srso_show_state() side effect |
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On Sun, Aug 20, 2023 at 06:18:58PM -0700, Josh Poimboeuf wrote: > 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> > --- > 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 f081d26616ac..bdd3e296f72b 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) >
Please put here a comment - something along the lines of:
"X86_FEATURE_IBPB_BRTYPE gets set as a result of the presence of the needed microcode so checking that is equivalent."
so that it is clear why it is ok to check this feature bit.
> 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) > --
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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