On Tue, 2011-05-10 at 17:38 +0200, Roedel, Joerg wrote: > On Tue, May 10, 2011 at 11:18:29AM -0400, Peter Zijlstra wrote: > > 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. > > By 'work' you mean that userspace can set it up but it doesn't count at > all in this situation? Right. > This would certainly be consistent behavior but I > can't imagine any use-case for it so that this code assumes that such a > situation is most likely a bug. > I can certainly change that if wanted, but I think its better to inform > userspace if we get weird values? The eternal how much rope to give and what knots to teach argument I guess. As it is, I think we allow people to exclude both user- and kernel-space, giving a similar situation, so allowing to exclude both host and guest is consistent. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
