Re: [PATCH 1/3] perf, core: Introduce attrs to count in eitherhost or guest mode

From: Peter Zijlstra
Date: Tue May 10 2011 - 11:15:33 EST


On Tue, 2011-05-10 at 16:59 +0200, Roedel, Joerg wrote:
> On Tue, May 10, 2011 at 10:45:46AM -0400, Peter Zijlstra wrote:
> > On Tue, 2011-05-10 at 16:35 +0200, Joerg Roedel wrote:
> > > + /* Can't exclude counting in guest and in host mode */
> > > + if (attr.exclude_host && attr.exclude_guest)
> > > + return -EINVAL;
> >
> > Why not?
>
> By definition the counter won't count at all. The hardware just ignores
> the bits if they are both set. My rationale here was that it does not
> makes sense to setup a counter and exclude guest and host mode.

I would expect it to 'work' but simply return 0. If that isn't what the
AMD hardware does you need to fix that in the AMD driver.

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