Re: [Qemu-devel] [Qemu-ppc] KVM-PR is broken with current QEMU

[David Gibson]

On Wed, Sep 21, 2016 at 10:22:11AM +0200, Thomas Huth wrote:
> On 20.09.2016 16:39, Cédric Le Goater wrote:
> > On 09/20/2016 04:24 PM, Thomas Huth wrote:
> >> On 20.09.2016 16:04, Cédric Le Goater wrote:
> [...]
> >>> There are other issues after in the guest (kernel crashing). But I think
> >>> these are related to TM which is not supported in KVM-PR. I am not sure
> >>> where we are on that point.
> >>
> >> There was a patch some months ago:
> >>
> >> https://lists.gnu.org/archive/html/qemu-ppc/2016-04/msg00046.html
> >>
> >> ... but I think it has never been included, as far as I can see.
> > 
> > and with that patch, the guest fully boots. But David had some concerns
> > on the way it is done. It would be nice to put some cycle on this. 
> 
> Looking at the mail thread, I think TM should be currently disabled for
> both, KVM-PR and TCG, i.e. only enabled for KVM-HV. The TM support in
> TCG is just fake, since TBEGIN always fails.

Right.  So there's two questions here

1) Is qemu correctly advertising availability of TM in the device
tree?

If not we need to fix that, which might involve adding a kernel
capability for the PR case.

2) Is the kvm unit test properly checking for availability of TM
before executing?

> Once we've got proper TM support in TCG, this can be easily changed
> within QEMU. And once we've got TM support in KVM-PR, I think we should
> also introduce a capability flag to KVM which can be used to inform QEMU
> about this.
> 
> So I think Anton's patch currently just lacks the check for TCG.
> Anton, if you've got some spare minutes, could you maybe send an updated
> version of that patch?

Sorry, which patch of Anton's?

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

signature.asc
Description: PGP signature