Messages in this thread | | | Date | Wed, 23 Aug 2023 16:02:22 -0700 | From | Josh Poimboeuf <> | Subject | Re: [PATCH 05/22] x86/srso: Fix SBPB enablement for mitigations=off |
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On Sun, Aug 20, 2023 at 06:19:02PM -0700, Josh Poimboeuf wrote: > If the user has requested no mitigations with mitigations=off, use the > lighter-weight SBPB instead of IBPB for other mitigations. > > Note that even with mitigations=off, IBPB/SBPB may still be used for > Spectre v2 user <-> user protection. Whether that makes sense is a > question for another day. > > Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation") > Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> > --- > arch/x86/kernel/cpu/bugs.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > index 10499bcd4e39..ff5bfe8f0ee9 100644 > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -2496,8 +2496,7 @@ static void __init srso_select_mitigation(void) > pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode")); > > pred_cmd: > - if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) && > - boot_cpu_has(X86_FEATURE_SBPB)) > + if (boot_cpu_has(X86_FEATURE_SBPB) && srso_mitigation == SRSO_MITIGATION_NONE) > x86_pred_cmd = PRED_CMD_SBPB;
Actually, I remembered this patch had another purpose. On future HW, if SRSO_NO is not set by the HW (which Boris said might be the case), and the SRSO bug bit is not set, then SBPB needs to be set.
I may just get rid of this label altogether and just hard-code the setting of x86_pred_cmd in the two places where it's needed.
-- Josh
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