Re: [PATCH 1/3] cpu/bugs: Fix selecting Automatic IBRS using spectre_v2=eibrs

[Jim Mattson]

On Tue, Feb 24, 2026 at 10:23 AM Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
>
> On 2/24/26 10:01, Kim Phillips wrote:
> > @@ -2136,7 +2136,8 @@ static void __init spectre_v2_select_mitigation(void)
> >       if ((spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS ||
> >            spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_LFENCE ||
> >            spectre_v2_cmd == SPECTRE_V2_CMD_EIBRS_RETPOLINE) &&
> > -         !boot_cpu_has(X86_FEATURE_IBRS_ENHANCED)) {
> > +         !(boot_cpu_has(X86_FEATURE_IBRS_ENHANCED) ||
> > +           boot_cpu_has(X86_FEATURE_AUTOIBRS))) {
> >               pr_err("EIBRS selected but CPU doesn't have Enhanced or Automatic IBRS. Switching to AUTO select\n");
> >               spectre_v2_cmd = SPECTRE_V2_CMD_AUTO;
> >       }
>
> Didn't we agree to just use the "Intel feature" name?

Aren't they quite different? IIRC, IBRS_ENHANCED protects host
userspace from guest indirect branch steering (i.e. VMSCAPE style
attacks), but AUTOIBRS does not.