RE: [PATCH v4 17/36] Documentation/x86: Document the new attack vector controls

[Kaplan, David]

[AMD Official Use Only - AMD Internal Distribution Only]

> -----Original Message-----
> From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Sent: Thursday, April 10, 2025 1:15 PM
> To: Kaplan, David <David.Kaplan@xxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Borislav Petkov <bp@xxxxxxxxx>;
> Peter Zijlstra <peterz@xxxxxxxxxxxxx>; Pawan Gupta
> <pawan.kumar.gupta@xxxxxxxxxxxxxxx>; Ingo Molnar <mingo@xxxxxxxxxx>; Dave
> Hansen <dave.hansen@xxxxxxxxxxxxxxx>; x86@xxxxxxxxxx; H . Peter Anvin
> <hpa@xxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Brendan Jackman
> <jackmanb@xxxxxxxxxx>; Derek Manwaring <derekmn@xxxxxxxxxx>
> Subject: Re: [PATCH v4 17/36] Documentation/x86: Document the new attack
> vector controls
>
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> On Mon, Mar 10, 2025 at 11:40:04AM -0500, David Kaplan wrote:
> > +=============== ============== ============ =============
> ============== ============
> > +Vulnerability   User-to-Kernel User-to-User Guest-to-Host Guest-to-Guest
> Cross-Thread
> > +=============== ============== ============ =============
> ============== ============
> > +BHI                   X                           X
> > +GDS                   X              X            X              X        (Note 1)
> > +L1TF                  X                           X                       (Note 2)
> > +MDS                   X              X            X              X        (Note 2)
> > +MMIO                  X              X            X              X        (Note 2)
> > +Meltdown              X
> > +Retbleed              X                           X                       (Note 3)
> > +RFDS                  X              X            X              X
> > +Spectre_v1            X
> > +Spectre_v2            X                           X
> > +Spectre_v2_user                      X                           X        (Note 1)
> > +SRBDS                 X              X            X              X
> > +SRSO                  X                           X
> > +SSB (Note 4)
>
> Any reason not to put the "Note 4" in the same column as the others?
>

The other notes are about cross-thread mitigation specifically and those notes refer to the SMT aspects of those issues.

Note 4 in this case is about the SSB vulnerability itself, explaining that by default there is no mitigation for any case.  I was concerned that including SSB but without any X's in any of the columns would be confusing, so the note attempted to explain that there were no default mitigations for SSB under any attack vector.

--David Kaplan