Re: [PATCH v3 4/5] KVM: ioeventfd for virtio-ccw devices.

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

On Tue, 26 Feb 2013 12:55:36 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Mon, Feb 25, 2013 at 04:27:49PM +0100, Cornelia Huck wrote:
> > Enhance KVM_IOEVENTFD with a new flag that allows to attach to virtio-ccw
> > devices on s390 via the KVM_VIRTIO_CCW_NOTIFY_BUS.
> > 
> > Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> > ---
> >  Documentation/virtual/kvm/api.txt |  8 ++++++++
> >  include/uapi/linux/kvm.h          |  3 +++
> >  virt/kvm/eventfd.c                | 14 ++++++++++++--
> >  3 files changed, 23 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> > index c2534c3..86232d6 100644
> > --- a/Documentation/virtual/kvm/api.txt
> > +++ b/Documentation/virtual/kvm/api.txt
> > @@ -1468,15 +1468,23 @@ struct kvm_ioeventfd {
> >  	__u8  pad[36];
> >  };
> >  
> > +For the special case of virtio-ccw devices on s390, the ioevent is matched
> > +to a subchannel/virtqueue tuple instead.
> > +
> >  The following flags are defined:
> >  
> >  #define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
> >  #define KVM_IOEVENTFD_FLAG_PIO       (1 << kvm_ioeventfd_flag_nr_pio)
> >  #define KVM_IOEVENTFD_FLAG_DEASSIGN  (1 << kvm_ioeventfd_flag_nr_deassign)
> > +#define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
> > +	(1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify)
> >  
> >  If datamatch flag is set, the event will be signaled only if the written value
> >  to the registered address is equal to datamatch in struct kvm_ioeventfd.
> >  
> > +For virtio-ccw devices, addr contains the subchannel id and datamatch the
> > +virtqueue index.
> > +
> >  
> >  4.60 KVM_DIRTY_TLB
> >  
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 9a2db57..8f3e5ae 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -448,12 +448,15 @@ enum {
> >  	kvm_ioeventfd_flag_nr_datamatch,
> >  	kvm_ioeventfd_flag_nr_pio,
> >  	kvm_ioeventfd_flag_nr_deassign,
> > +	kvm_ioeventfd_flag_nr_virtio_ccw_notify,
> >  	kvm_ioeventfd_flag_nr_max,
> >  };
> >  
> >  #define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
> >  #define KVM_IOEVENTFD_FLAG_PIO       (1 << kvm_ioeventfd_flag_nr_pio)
> >  #define KVM_IOEVENTFD_FLAG_DEASSIGN  (1 << kvm_ioeventfd_flag_nr_deassign)
> > +#define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
> > +	(1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify)
> >  
> >  #define KVM_IOEVENTFD_VALID_FLAG_MASK  ((1 << kvm_ioeventfd_flag_nr_max) - 1)
> >  
> > diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> > index f0ced1a..8de3cd7 100644
> > --- a/virt/kvm/eventfd.c
> > +++ b/virt/kvm/eventfd.c
> > @@ -679,11 +679,16 @@ static int
> >  kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
> >  {
> >  	int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
> > -	enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
> > +	int                       ccw;
> > +	enum kvm_bus              bus_idx;
> >  	struct _ioeventfd        *p;
> >  	struct eventfd_ctx       *eventfd;
> >  	int                       ret;
> >  
> > +	ccw = args->flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY;
> > +	bus_idx = pio ? KVM_PIO_BUS :
> > +		ccw ? KVM_VIRTIO_CCW_NOTIFY_BUS :
> > +		KVM_MMIO_BUS;
> 
> May be better to rewrite using if/else.

Matter of taste, I guess. But I can do that.

> 
> >  	/* must be natural-word sized */
> >  	switch (args->len) {
> >  	case 1:
> > @@ -759,11 +764,16 @@ static int
> >  kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
> >  {
> >  	int                       pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
> > -	enum kvm_bus              bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
> > +	int                       ccw;
> > +	enum kvm_bus              bus_idx;
> >  	struct _ioeventfd        *p, *tmp;
> >  	struct eventfd_ctx       *eventfd;
> >  	int                       ret = -ENOENT;
> >  
> > +	ccw = args->flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY;
> > +	bus_idx = pio ? KVM_PIO_BUS :
> > +		ccw ? KVM_VIRTIO_CCW_NOTIFY_BUS :
> > +		KVM_MMIO_BUS;
> >  	eventfd = eventfd_ctx_fdget(args->fd);
> >  	if (IS_ERR(eventfd))
> >  		return PTR_ERR(eventfd);
> > -- 
> > 1.7.12.4
>