Messages in this thread | | | Date | Mon, 19 Nov 2018 22:12:44 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [Patch v5 11/16] x86/speculation: Add Spectre v2 app to app protection modes |
| |
On Mon, 19 Nov 2018, Jiri Kosina wrote: > 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.
That and it can be split in pieces so it actually becomes reviewable.
Thanks,
tglx
| |