Re: [PATCH v7 27/27] KVM: arm64/sve: Document KVM API extensions for SVE

Dave Martin
2019-04-10T12:34:18Z

On Fri, Apr 05, 2019 at 05:38:04PM +0200, Andrew Jones wrote:
> On Fri, Apr 05, 2019 at 02:00:07PM +0100, Dave Martin wrote:
> > On Fri, Apr 05, 2019 at 12:39:37PM +0200, Andrew Jones wrote:
> > > On Fri, Apr 05, 2019 at 10:36:17AM +0100, Dave Martin wrote:
> > > > On Thu, Apr 04, 2019 at 11:09:21PM +0200, Andrew Jones wrote:

[...]

> > > > > I'm still not sure about EPERM vs. ENOEXEC.
> > > >
> > > > There is no need to distinguish the two: this is just a generic "vcpu in
> > > > wrong state for this to work" error. I can't think of another subsystem
> > > > that uses ENOEXEC for this meaning, but it's established in KVM.
> > > >
> > > > If you can't see a reason why we would need these to be distinct
> > > > errors (?) then I'm happy for this to be ENOEXEC for all cases.
> > > >
> > >
> > > I do see some value in keeping them distinct. I think it's just the use
> > > of EPERM specifically that bothers me, but I don't have that strong of
> > > an opinion against its use either. So I'll just shut up :)
> >
> > In an earlier incarnation I had EBADFD, which does kind of mean the
> > right thing.
> >
> > If there's not a clear way forward, I may leave this all as-is for now
> > (but I'll remove the explicit documentation for KVM_{GET,SET}_ONE_REG
> > error codes to give us more flexibility about this in the future, as
> > discussed).
> >
> > Any objection?
>
> Nope. Let's do that. EBADFD doesn't sound good, because we're using the FD
> without trouble before and even after we attempt these ioctls. I think
> EBADFD would indicate that no future ioctl (or read,write) should be
> expected to work.

OK. I may also keep some of the error code documentation, but water it
down a bit to make it clearer that the error codes are indicate and
arm64-specifc.

We can see how it looks when I have a series to post.

Cheers
---Dave