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SubjectRe: [PATCH] x86/bugs: Switch to "auto" when "ibrs" selected on Enhanced IBRS parts
On Thu, Jul 14, 2022 at 07:03:32PM +0200, Peter Zijlstra wrote:
> On Thu, Jul 14, 2022 at 09:01:06AM -0700, Josh Poimboeuf wrote:
>
> > > Yeah this; if the user asks for IBRS, we should give him IBRS. I hate
> > > the 'I know better, let me change that for you' mentality.
> >
> > eIBRS CPUs don't even have legacy IBRS so I don't see how this is even
> > possible.
>
> You can still WRMSR a lot on them. Might not make sense but it 'works'.

Even in Intel documentation, eIBRS is often referred to as IBRS. It
wouldn't be surprising for a user to consider spectre_v2=ibrs to mean
"use eIBRS".

I'm pretty sure there's nobody out there that wants spectre_v2=ibrs to
mean "make it slower and possibly less secure because it's being used
contrary to the spec".

--
Josh

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