Re: [Xen-devel] [PATCH v15 17/21] x86/VPMU: Handle PMU interrupts for PV guests

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 11/25/2014 09:28 AM, Jan Beulich wrote:
> > +            else
> > +            {
> > +                struct segment_register seg;
> > +
> > +                hvm_get_segment_register(sampled, x86_seg_cs, &seg);
> > +                r->cs = seg.sel;
> > +                hvm_get_segment_register(sampled, x86_seg_ss, &seg);
> > +                r->ss = seg.sel;
> > +                if ( seg.attr.fields.dpl != 0 )
> > +                    *flags |= PMU_SAMPLE_USER;
> Is that how hardware treats it (CPL != 0 meaning user, rather
> than CPL == 3)?
You mean how *software* (e.g. Linux kernel) treats it? If yes, then for 
32-bit user_mode() checks for (CS == 3) and for 64-bit it's !!(CS & 3).
> Maybe you should surface CPL instead of a
> boolean flag?
Am I not already doing it by passing SS and CS to the guest?

-boris

> Anyway, with or without the adjustments (unless you go a 3rd
> way)
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>
> Jan

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