Re: [PATCH] add tlbi=off to disable INVLPGB

[Peter Zijlstra]

On Thu, Jul 30, 2026 at 11:24:39AM -0700, Borislav Petkov wrote:
> On Thu, Jul 30, 2026 at 07:31:04PM +0200, Peter Zijlstra wrote:
> > But also, nah:
> > 
> >   https://support.arm.com/documentation/dui0802/b/A64-General-Instructions/TLBI
> > 
> > "TLBI - TLB invalidate operation."
> 
> Yap, that's what I meant.
> 
> >   tlbi={ipi,broadcast}
> > 
> > Anyway, INVLPGB stands for INVaLidate PaGe Broadcast, ain'ted that hard
> > :-) Also, you know who to complain to for that instruction :-)
> 
> Too late for that. :)
> 
> "tlbi=broadcast" is a bit much to type: imagine you're hunched over some box
> in the server room, like Spiderman, crouching between racks and balancing the
> keyboard on some old pile of cables... :-P

There is IPMI and other fancy remote management stuff these days. There
is no reason to suffer hearing loss for entering server rooms anymore
:-)

> So how about shorter:
> 
> "tlbi=bcast"
> "tlbi=ipi"
> 
> ?
> 
> We probably won't need to write "bcast" at all, actually, because that would
> be the default. So "tlbi=ipi" only. Yeah, that's good.

Didn't we have a case where INVLPGB was disabled due to firmware or
something? I was thinking tlbi=broadcast could be used to force enable
it or something.

Anyway, if that case don't exist, then yeah.