Re: [PATCH v2 2/2] x86/bugs: Don't fill RSB on context switch with eIBRS

[Josh Poimboeuf]

On Thu, Nov 21, 2024 at 12:07:19PM -0800, Josh Poimboeuf wrote:
> User->user Spectre v2 attacks (including RSB) across context switches
> are already mitigated by IBPB in cond_mitigation(), if enabled globally
> or if either the prev or the next task has opted in to protection.  RSB
> filling without IBPB serves no purpose for protecting user space, as
> indirect branches are still vulnerable.

Question for Intel/AMD folks: where is it documented that IBPB clears
the RSB?  I thought I'd seen this somewhere but I can't seem to find it.

-- 
Josh