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

["Michael S. Tsirkin" <mst@redhat.com>]

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.

>  	/* 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