Re: [RFC PATCH v2 3/4] KVM: ioeventfd for s390 css devices.

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

On Sun, 24 Feb 2013 11:47:50 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Fri, Feb 22, 2013 at 01:09:48PM +0100, Cornelia Huck wrote:
> > Enhance KVM_IOEVENTFD with a new flag that allows to attach to s390 css
> > devices.
> > 
> > Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> > ---
> >  Documentation/virtual/kvm/api.txt | 7 +++++++
> >  include/uapi/linux/kvm.h          | 2 ++
> >  virt/kvm/eventfd.c                | 8 ++++++--
> >  3 files changed, 15 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> > index c2534c3..40e799c 100644
> > --- a/Documentation/virtual/kvm/api.txt
> > +++ b/Documentation/virtual/kvm/api.txt
> > @@ -1468,15 +1468,22 @@ struct kvm_ioeventfd {
> >  	__u8  pad[36];
> >  };
> >  
> > +For the special case of s390 css devices, 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_CSS       (1 << kvm_ioeventfd_flag_nr_css)
> >  
> >  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 css 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..1df0766 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -448,12 +448,14 @@ enum {
> >  	kvm_ioeventfd_flag_nr_datamatch,
> >  	kvm_ioeventfd_flag_nr_pio,
> >  	kvm_ioeventfd_flag_nr_deassign,
> > +	kvm_ioeventfd_flag_nr_css,
> >  	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_CSS       (1 << kvm_ioeventfd_flag_nr_css)
> 
> So let's explicitly name is KVM_IOEVENTFD_S390_VIRTIO_CCW or even
> KVM_IOEVENTFD_S390_VIRTIO_CCW_NOTIFY?

How about KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY?

> Also, maybe we want to add KVM_IOEVENTFD_S390_VIRTIO_NOTIFY as well?

No, since s390-virtio is a dead end.

> 
> >  
> >  #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..7347652 100644
> > --- a/virt/kvm/eventfd.c
> > +++ b/virt/kvm/eventfd.c
> > @@ -679,11 +679,13 @@ 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                       css = args->flags & KVM_IOEVENTFD_FLAG_CSS;
> > +	enum kvm_bus              bus_idx;
> >  	struct _ioeventfd        *p;
> >  	struct eventfd_ctx       *eventfd;
> >  	int                       ret;
> >  
> > +	bus_idx = pio ? KVM_PIO_BUS : css ? KVM_CSS_BUS: KVM_MMIO_BUS;
> >  	/* must be natural-word sized */
> >  	switch (args->len) {
> >  	case 1:
> > @@ -759,11 +761,13 @@ 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                       css = args->flags & KVM_IOEVENTFD_FLAG_CSS;
> > +	enum kvm_bus              bus_idx;
> >  	struct _ioeventfd        *p, *tmp;
> >  	struct eventfd_ctx       *eventfd;
> >  	int                       ret = -ENOENT;
> >  
> > +	bus_idx = pio ? KVM_PIO_BUS : css ? KVM_CSS_BUS: KVM_MMIO_BUS;
> >  	eventfd = eventfd_ctx_fdget(args->fd);
> >  	if (IS_ERR(eventfd))
> >  		return PTR_ERR(eventfd);
> > -- 
> > 1.7.12.4
>