Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-04 Thread Tim Chen
On 12/04/2018 09:20 AM, Linus Torvalds wrote: >> STIBP >> ^ >> Implementations of STIBP on existing Core-family processors (where STIBP >> functionality was added through a microcode update) work by disabling >> branch predictors that both: >> >> 1. Contain indirect branch predictions for

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-04 Thread Dave Hansen
> static const char * const spectre_v2_user_strings[] = { > [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", > [SPECTRE_V2_USER_STRICT]= "User space: Mitigation: STIBP > protection", > [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via >

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-04 Thread Linus Torvalds
On Mon, Dec 3, 2018 at 5:38 PM Tim Chen wrote: > > To make the usage of STIBP and its working principles clear, > here are some additional explanations of STIBP from our Intel > HW architects. This should also help answer some of the questions > from Thomas and others on STIBP's usages with IBPB

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-04 Thread Arjan van de Ven
On processors with enhanced IBRS support, we recommend setting IBRS to 1 and left set. Then why doesn't CPU with EIBRS support acutally *default* to '1', with opt-out possibility for OS? (slightly longer answer) you can pretty much assume that on these CPUs, IBRS doesn't actually do anything

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-04 Thread Arjan van de Ven
On processors with enhanced IBRS support, we recommend setting IBRS to 1 and left set. Then why doesn't CPU with EIBRS support acutally *default* to '1', with opt-out possibility for OS? the BIOSes could indeed get this set up this way. do you want to trust the bios to get it right?

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-04 Thread Jiri Kosina
On Mon, 3 Dec 2018, Tim Chen wrote: > > Can we please just fix this stupid lie? > > > > Yes, Intel calls it "STIBP" and tries to make it out to be about the > > indirect branch predictor being per-SMT thread. > > > > But the reason it is unacceptable is apparently because in reality it just > >

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-12-03 Thread Tim Chen
On 11/25/2018 12:40 PM, Linus Torvalds wrote: > [ You forgot to fix your quilt setup.. ] > > On Sun, 25 Nov 2018, Thomas Gleixner wrote: >> >> The mitigation guide documents how STIPB works: >> >>Setting bit 1 (STIBP) of the IA32_SPEC_CTRL MSR on a logical processor >>prevents the

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-26 Thread Tim Chen
On 11/26/2018 01:52 PM, Lendacky, Thomas wrote: > On 11/26/2018 02:58 PM, Thomas Gleixner wrote: >> On Mon, 26 Nov 2018, Andrea Arcangeli wrote: >> >>> Hello, >>> >>> On Sun, Nov 25, 2018 at 11:28:59PM +0100, Thomas Gleixner wrote: Indeed. Just checked the documentation again, it's also not

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-26 Thread Lendacky, Thomas
On 11/26/2018 02:58 PM, Thomas Gleixner wrote: > On Mon, 26 Nov 2018, Andrea Arcangeli wrote: > >> Hello, >> >> On Sun, Nov 25, 2018 at 11:28:59PM +0100, Thomas Gleixner wrote: >>> Indeed. Just checked the documentation again, it's also not clear whether >>> IBPB is required if STIPB is in use.

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-26 Thread Thomas Gleixner
On Mon, 26 Nov 2018, Andrea Arcangeli wrote: > Hello, > > On Sun, Nov 25, 2018 at 11:28:59PM +0100, Thomas Gleixner wrote: > > Indeed. Just checked the documentation again, it's also not clear whether > > IBPB is required if STIPB is in use. > > I tried to ask this question too earlier: > >

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-26 Thread Andrea Arcangeli
Hello, On Sun, Nov 25, 2018 at 11:28:59PM +0100, Thomas Gleixner wrote: > Indeed. Just checked the documentation again, it's also not clear whether > IBPB is required if STIPB is in use. I tried to ask this question too earlier: https://lkml.kernel.org/r/20181119234528.gj29...@redhat.com If

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-26 Thread Ingo Molnar
* Thomas Gleixner wrote: > On Sun, 25 Nov 2018, Linus Torvalds wrote: > > > [ You forgot to fix your quilt setup.. ] > > Duh. Should have pinned that package. > > > On Sun, 25 Nov 2018, Thomas Gleixner wrote: > > > > > > The mitigation guide documents how STIPB works: > > > > > >Setting

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-25 Thread Thomas Gleixner
On Sun, 25 Nov 2018, Linus Torvalds wrote: > [ You forgot to fix your quilt setup.. ] Duh. Should have pinned that package. > On Sun, 25 Nov 2018, Thomas Gleixner wrote: > > > > The mitigation guide documents how STIPB works: > > > >Setting bit 1 (STIBP) of the IA32_SPEC_CTRL MSR on a

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-25 Thread Jiri Kosina
On Sun, 25 Nov 2018, Linus Torvalds wrote: > > The mitigation guide documents how STIPB works: > > > >Setting bit 1 (STIBP) of the IA32_SPEC_CTRL MSR on a logical processor > >prevents the predicted targets of indirect branches on any logical > >processor of that core from being

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-25 Thread Linus Torvalds
[ You forgot to fix your quilt setup.. ] On Sun, 25 Nov 2018, Thomas Gleixner wrote: > > The mitigation guide documents how STIPB works: > >Setting bit 1 (STIBP) of the IA32_SPEC_CTRL MSR on a logical processor >prevents the predicted targets of indirect branches on any logical >

Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-25 Thread Randy Dunlap
Hi, Can you alter this without publishing a v3? (see below) On 11/25/18 10:33 AM, Thomas Gleixner wrote: > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4241,9 +4241,16 @@ > per thread. The

[patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

2018-11-25 Thread Thomas Gleixner
If 'prctl' mode of user space protection from spectre v2 is selected on the kernel command-line, STIBP and IBPB are applied on tasks which restrict their indirect branch speculation via prctl. SECCOMP enables the SSBD mitigation for sandboxed tasks already, so it makes sense to prevent spectre v2