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

Michael S. Tsirkin
2013-02-26T10:55:36Z

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