Re: [RFC PATCH v2 4/4] KVM: s390: Wire up ioeventfd.

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Sun, 24 Feb 2013 11:45:22 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Fri, Feb 22, 2013 at 01:09:49PM +0100, Cornelia Huck wrote:
> > Enable ioeventfd support on s390 and hook up diagnose 500 virtio-ccw
> > notifications.
> > 
> > Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> > ---
> >  arch/s390/kvm/Kconfig    |  1 +
> >  arch/s390/kvm/Makefile   |  2 +-
> >  arch/s390/kvm/diag.c     | 25 +++++++++++++++++++++++++
> >  arch/s390/kvm/kvm-s390.c |  1 +
> >  4 files changed, 28 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
> > index b58dd86..3c43e30 100644
> > --- a/arch/s390/kvm/Kconfig
> > +++ b/arch/s390/kvm/Kconfig
> > @@ -22,6 +22,7 @@ config KVM
> >  	select PREEMPT_NOTIFIERS
> >  	select ANON_INODES
> >  	select HAVE_KVM_CPU_RELAX_INTERCEPT
> > +	select HAVE_KVM_EVENTFD
> >  	---help---
> >  	  Support hosting paravirtualized guest machines using the SIE
> >  	  virtualization capability on the mainframe. This should work
> > diff --git a/arch/s390/kvm/Makefile b/arch/s390/kvm/Makefile
> > index 3975722..8fe9d65 100644
> > --- a/arch/s390/kvm/Makefile
> > +++ b/arch/s390/kvm/Makefile
> > @@ -6,7 +6,7 @@
> >  # it under the terms of the GNU General Public License (version 2 only)
> >  # as published by the Free Software Foundation.
> >  
> > -common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o)
> > +common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o eventfd.o)
> >  
> >  ccflags-y := -Ivirt/kvm -Iarch/s390/kvm
> >  
> > diff --git a/arch/s390/kvm/diag.c b/arch/s390/kvm/diag.c
> > index a390687..13cf74a 100644
> > --- a/arch/s390/kvm/diag.c
> > +++ b/arch/s390/kvm/diag.c
> > @@ -104,6 +104,29 @@ static int __diag_ipl_functions(struct kvm_vcpu *vcpu)
> >  	return -EREMOTE;
> >  }
> >  
> > +static int __diag_virtio_hypercall(struct kvm_vcpu *vcpu)
> > +{
> > +	int ret, idx;
> > +
> > +	/* No virtio-ccw notification? Get out quickly. */
> > +	if (!vcpu->kvm->arch.css_support ||
> > +	    (vcpu->run->s.regs.gprs[1] != 3))
> > +		return -EOPNOTSUPP;
> 
> Looks like we have:
> arch/s390/include/uapi/asm/kvm_virtio.h:#define KVM_S390_VIRTIO_NOTIFY 0
> arch/s390/include/uapi/asm/kvm_virtio.h:#define KVM_S390_VIRTIO_RESET 1
> arch/s390/include/uapi/asm/kvm_virtio.h:#define KVM_S390_VIRTIO_SET_STATUS      2
> 
> KVM_S390_VIRTIO_CSS_NOTIFY is missing? Strange.
> Maybe it should be added in that header and included here?

kvm_virtio.h is for the old-style s390-virtio mechanism. Subcode 3 will
be included in 3.9.

> Do some guests use it?
> Also, do you want to support KVM_S390_VIRTIO_NOTIFY as well?

We don't want to invest any more effort in the old style s390-virtio
transport (other than keeping it working). Any future work will be for
virtio-ccw.

> 
> 
> > +
> > +	idx = srcu_read_lock(&vcpu->kvm->srcu);
> > +	/*
> > +	 * The layout is as follows:
> > +	 * - gpr 2 contains the subchannel id (passed as addr)
> > +	 * - gpr 3 contains the virtqueue index (passed as datamatch)
> > +	 */
> > +	ret = kvm_io_bus_write(vcpu->kvm, KVM_CSS_BUS,
> > +				vcpu->run->s.regs.gprs[2],
> > +				8, &vcpu->run->s.regs.gprs[3]);
> > +	srcu_read_unlock(&vcpu->kvm->srcu, idx);
> > +	/* kvm_io_bus_write returns -EOPNOTSUPP if it found no match. */
> > +	return ret;
> > +}
> > +
> >  int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
> >  {
> >  	int code = (vcpu->arch.sie_block->ipb & 0xfff0000) >> 16;
> > @@ -118,6 +141,8 @@ int kvm_s390_handle_diag(struct kvm_vcpu *vcpu)
> >  		return __diag_time_slice_end_directed(vcpu);
> >  	case 0x308:
> >  		return __diag_ipl_functions(vcpu);
> > +	case 0x500:
> > +		return __diag_virtio_hypercall(vcpu);
> >  	default:
> >  		return -EOPNOTSUPP;
> >  	}
> > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> > index f822d36..04d2454 100644
> > --- a/arch/s390/kvm/kvm-s390.c
> > +++ b/arch/s390/kvm/kvm-s390.c
> > @@ -142,6 +142,7 @@ int kvm_dev_ioctl_check_extension(long ext)
> >  	case KVM_CAP_ONE_REG:
> >  	case KVM_CAP_ENABLE_CAP:
> >  	case KVM_CAP_S390_CSS_SUPPORT:
> > +	case KVM_CAP_IOEVENTFD:
> >  		r = 1;
> >  		break;
> >  	case KVM_CAP_NR_VCPUS:
> > -- 
> > 1.7.12.4
>