Messages in this thread | | | Subject | Re: [PATCH v5 2/2] x86/speculation: Enable cross-hyperthread spectre v2 STIBP mitigation | From | Tom Lendacky <> | Date | Thu, 13 Sep 2018 09:53:03 -0500 |
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On 09/12/2018 04:26 PM, Tim Chen wrote: > On 09/12/2018 10:16 AM, Tom Lendacky wrote: >> >> >> On 09/11/2018 04:16 PM, Thomas Gleixner wrote: >>> On Tue, 11 Sep 2018, Tim Chen wrote: >>>> On 09/10/2018 04:46 AM, Jiri Kosina wrote: >>>>> Nah, IBPB is actuall there, sorry. So I'll add reporting of STIBP + fixup >>>>> the missing reporting of RSB_CTXSW for v6. >>>>> >>>> >>>> I anticipate that STIBP could affect workloads with a lot of indirect >>>> branches (see previous discussion with Andrea). We should have a >>>> knob for people to opt in or opt out of STIBP. >>> >>> Feel free to send a patch to that effect. >> >> Tim, are you planning on sending a patch for this? If so, what type of >> opt in/out are you thinking about, something similar to SSBD? >> > > I'm working on a patch for choosing the Spectre v2 app to app > mitigation option. > > Something like the following: > > enum spectre_v2_app2app_mitigation { > SPECTRE_V2_APP2APP_NONE, > SPECTRE_V2_APP2APP_LITE, > SPECTRE_V2_APP2APP_IBPB, > SPECTRE_V2_APP2APP_STIBP, > SPECTRE_V2_APP2APP_STRICT, > }; > > static const char *spectre_v2_app2app_strings[] = { > [SPECTRE_V2_APP2APP_NONE] = "App-App Vulnerable", > [SPECTRE_V2_APP2APP_LITE] = "App-App Mitigation: Protect only non-dumpable process", > [SPECTRE_V2_APP2APP_IBPB] = "App-App Mitigation: Protect app against attack from same cpu", > [SPECTRE_V2_APP2APP_STIBP] = "App-App Mitigation: Protect app against attack from sibling cpu", > [SPECTRE_V2_APP2APP_STRICT] = "App-App Mitigation: Full app to app attack protection", > }; > > So the APP2APP_LITE protection's intention is to turn on STIBP and IBPB for non-dumpable > process. But in my first version I may limit it to IBPB as choosing > STIBP based on process characteristics will require some frobbing of > the flags as what we've done in SSBD. That will require more careful > work and tests. > > The STRICT option will turn STIBP on always and IBPB always on > non-ptraceable context switches. > > Is this something reasonable? > > Tom, if you already have a patch, feel free to post.
No, I don't have anything. I just like the idea of opt in/out for STIBP and thought it should be similar to SSBD to provide consistency.
Thanks, Tom
> > Tim >
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