Messages in this thread | | | Date | Wed, 17 Apr 2024 16:14:26 +0100 | Subject | Re: [PATCH v3] x86/bugs: Only harden syscalls when needed | From | Andrew Cooper <> |
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On 17/04/2024 12:02 am, Josh Poimboeuf wrote: > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > index ca295b0c1eee..dcb97cc2758f 100644 > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -1678,6 +1687,21 @@ static void __init spectre_v2_select_mitigation(void) > enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline(); > enum spectre_v2_mitigation mode = SPECTRE_V2_NONE; > > + /* > + * X86_FEATURE_INDIRECT_SAFE indicates whether indirect calls can be > + * considered safe. That means either: > + * > + * - the CPU isn't vulnerable to Spectre v2 or its variants; > + * > + * - a hardware mitigation is in place (e.g., IBRS, BHI_DIS_S); or > + * > + * - the user turned off mitigations altogether. > + * > + * Assume innocence until proven guilty: set the cap bit now, then > + * clear it later if/when needed. > + */ > + setup_force_cpu_cap(X86_FEATURE_INDIRECT_SAFE);
Following on from the (re)discovery that X86_FEATURE_RETPOLINE is a poor name given what it *actually* does, can I recommend s/SAFE/OK/ here?
This flag really is "do I want indirect branches or not", which - as noted here - is more than just a judgement of whether indirect branches are "safe".
~Andrew
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