Re: [Qemu-devel] [PATCH] hw/arm/virt: Reject gic-version=host for non-KVM

[Richard W.M. Jones]

On Fri, Jun 17, 2016 at 03:49:38PM +0100, Peter Maydell wrote:
> On 26 May 2016 at 15:53, Peter Maydell <address@hidden> wrote:
> > On 26 May 2016 at 15:46, Richard W.M. Jones <address@hidden> wrote:
> >> The problem with this is if I'm using TCG fallback mode, how
> >> can I specify the right gic-version?  ie:
> >>
> >>   -M virt,gic-version=host,accel=kvm:tcg
> >>
> >> Only qemu knows if KVM is going to be enabled.
> >>
> >> The same problem happens with '-cpu host' BTW.  I really want a "make
> >> it work" option, as I've said on several previous occasions on this
> >> list eg:
> >> https://lists.nongnu.org/archive/html/qemu-devel/2014-08/msg04173.html
> >
> > I agree that we really need to do better here (thinking about
> > the problem is on my todo list but generally other more pressing
> > issues intervene). I'd welcome suggestions for semantics which
> > (a) do what you want (b) are reasonably in line with what we do
> > on other host architectures (c) don't break existing command lines.
> > (I think those are the main requirements.)
> 
> ...so does anybody have any concrete suggestions? We could fix
> this for 2.7 but we're starting to run low on time for that.

I have changed libguestfs so it tries to guess if KVM will be used or
not.  We have to do this for the -cpu option too, but the guess is not
too reliable.  Only QEMU has the actual knowledge we need.

https://github.com/libguestfs/libguestfs/commit/7023f20830a681ef36f8f99415fe41791555a3db

Can we not have a "give me a GIC which will work" option, eg.

  -M virt,gic-version=besteffort,accel=kvm:tcg

I don't care if it's not the fastest or most featureful.

Rich.

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