Re: MSR driver

H. Peter Anvin (hpa@transmeta.com)
14 Nov 1997 07:42:07 GMT

Followup to: <k2g1p0yn1p.fsf@zero.aec.at>
By author: Andi Kleen <ak@muc.de>
In newsgroup: linux.dev.kernel
> >
> > a) character device
> >
> > This is the currently implemented method.
> > It was criticized by Linus and I get the problem. I believe that
> > this way, it would be very easy to grant specific users access to
> > the MSR registers.
>
> Why was it criticized? IMHO it's the best solution because it gives
> all the flexibility of unix permissions for the access control.
> AFAIK OpenBSD does it the same way.
>

Only if you take SMP into account (this applies to all methods.) It's
no good if on an SMP machine you effectively end up setting MSR's on
any random processor, which may change without notice.

We may want to have a "cpu X only" system call (schedule only on a
specific processor) for things that use per-processor features, such
as RDTSC.)

-hpa

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