Re: UMIP and clearcpuid=

[Peter Zijlstra]

On Wed, Jun 10, 2026 at 04:55:01PM -0700, Borislav Petkov wrote:
> On Wed, Jun 10, 2026 at 08:41:02PM +0000, Ronan Pigott wrote:
> > My use case is playing Windows video games via Wine. For whatever reason,
> > they like to use these instructions:
> > 
> >   $ journalctl -b -g umip -o cat --since=-5m
> >   umip_printk: 117 callbacks suppressed
> >   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: SGDT instruction cannot be used by applications.
> >   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: For now, expensive software emulation returns the result.
> >   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fec20: SGDT instruction cannot be used by applications.
> >   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fec20: For now, expensive software emulation returns the result.
> >   umip: StreetFighter6.[3837] ip:15f523f4d sp:524fecb0: SGDT instruction cannot be used by applications.
> > 
> > I don't think I benefit from the UMIP protection or the emulation, so I'd
> 
> Question is, do you benefit from disabling the UMIP emulation. Any noticeable
> game performance increase?
> 
> > rather just disable it. clearcpuid still works, but results in a tainted
> > kernel etc:
> > 
> >   kernel: clearcpuid: force-disabling CPU feature flag: umip
> >   kernel: !!! setcpuid=/clearcpuid= in use, this is for TESTING ONLY, may break things horribly. Tainting kernel.
> 
> Right, I don't think a tainted kernel would be a problem but yeah...
> 
> I still think that it would make sense to issue a big fat warning when
> disabling UMIP so that people know.
>  
> > so I think a umip=no flag as originally proposed could be preferable. Would
> > that be acceptable?
> 
> umip=disable or umip=off
> 
> I guess.
> 
> Other than that, I guess that's a valid use case I'd say. Let's see what the
> others think.

So my own game box also has this; aside from the dmesg spam, there was
one game that just plain didn't run. I forgot what it was, but I'm sure
it was related to some dodgy DRM thing.

It is really annoying having to disable UMIP though, its bugged me, just
not enough to ever actually do anything about it.