Re: [PATCH] target/s390x/kvm: Enable adapter interruption suppression again

[Matthew Rosato]

On 1/16/20 8:22 AM, Christian Borntraeger wrote:
> On 16.01.20 13:55, Thomas Huth wrote:
> > On 16/01/2020 13.50, Cornelia Huck wrote:
> > > On Thu, 16 Jan 2020 13:20:26 +0100
> > > Thomas Huth <address@hidden> wrote:
> > >
> > > > The AIS feature has been disabled late in the v2.10 development
> > > > cycle since there were some issues with migration (see commit
> > > > 3f2d07b3b01ea61126b - "s390x/ais: for 2.10 stable: disable ais
> > > > facility"). We originally wanted to enable it again for newer
> > > > machine types, but apparently we forgot to do this so far. Let's
> > > > do it for the new s390-ccw-virtio-5.0 machine now.
> > > >
> > > > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1756946
> > > > Signed-off-by: Thomas Huth <address@hidden>
> > > > ---
> > > >   hw/s390x/s390-virtio-ccw.c         |  4 ++++
> > > >   include/hw/s390x/s390-virtio-ccw.h |  4 ++++
> > > >   target/s390x/kvm.c                 | 11 ++++++++---
> > > >   3 files changed, 16 insertions(+), 3 deletions(-)
> > >
> > > > @@ -365,10 +367,13 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
> > > >       /*
> > > >        * The migration interface for ais was introduced with kernel 4.13
> > > >        * but the capability itself had been active since 4.12. As migration
> > > > -     * support is considered necessary let's disable ais in the 2.10
> > > > -     * machine.
> > > > +     * support is considered necessary we only enable this for newer
> > >
> > > s/necessary we only enable this/necessary, we only try to enable this/
> > >
> > > > +     * machine types and if KVM_CAP_S390_AIS_MIGRATION is available.
> > >
> > > maybe s/and if/if/
> >
> > Sure ... could you fix it up when picking up the patch (in case I don't
> > have to respin), or do you want me to send a v2?
> >
> > > >        */
> > > > -    /* kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0); */
> > > > +    if (smc->kvm_ais_allowed &&
> > > > +        kvm_check_extension(s, KVM_CAP_S390_AIS_MIGRATION)) {
> > > > +        kvm_vm_enable_cap(s, KVM_CAP_S390_AIS, 0);
> > > > +    }
> > > >   
> > > >       kvm_set_max_memslot_size(KVM_SLOT_MAX_BYTES);
> > > >       return 0;
> > >
> > > Looks good.
> > >
> > > Remind me again: ais only made a difference for pci devices, right? Is
> > > it enough to give this a quick whirl with virtio-pci devices?
> >
> > I don't remember the details, Christian, could you please answer this
> > question?
>
> Yes, IIRC AIS was there for PCI, but not for Crypto or virtio.

This matches my understanding as well.

> The patch looks sane, but it would be good if someone could try
> the AIS stuff.
>
> Matt, can you have a look?

Sure.  But my PCI environment is currently down for a maintenance 
window, will try again later today.