Messages in this thread | | | Date | Mon, 19 Nov 2018 21:55:27 +0100 (CET) | From | Jiri Kosina <> | Subject | Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes |
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On Mon, 19 Nov 2018, Thomas Gleixner wrote:
> > @@ -452,12 +542,6 @@ static void __init spectre_v2_select_mitigation(void) > > setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW); > > pr_info("Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch\n"); > > > > - /* Initialize Indirect Branch Prediction Barrier if supported */ > > - if (boot_cpu_has(X86_FEATURE_IBPB)) { > > - setup_force_cpu_cap(X86_FEATURE_USE_IBPB); > > - pr_info("Spectre v2 mitigation: Enabling Indirect Branch Prediction Barrier\n"); > > - } > > - > > /* > > * Retpoline means the kernel is safe because it has no indirect > > * branches. Enhanced IBRS protects firmware too, so, enable restricted > > @@ -474,6 +558,43 @@ static void __init spectre_v2_select_mitigation(void) > > pr_info("Enabling Restricted Speculation for firmware calls\n"); > > } > > > > + app2app_mode = SPECTRE_V2_APP2APP_NONE; > > + if (!boot_cpu_has(X86_FEATURE_IBPB) || > > + !boot_cpu_has(X86_FEATURE_STIBP)) > > + goto set_app2app_mode; > > So before that change IBPB was usable without STIBP, now not longer. What's > the rationale? > > This patch changes a gazillion things at once and is completely > unreviewable.
The patchset actually ties together IBPB and STIBP pretty closely, which is IMO a good thing; there is no good reason why anone would want just one of those (or each in a different mode), at least before this magical coscheduling exists.
But I guess this fact should be documented somewhere.
-- Jiri Kosina SUSE Labs
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