On 26/02/13 12:18, Michael S. Tsirkin wrote:
> virtio_ccw: pass a cookie value to kvm hypercall
>
> Lookups by channel/vq pair on host during virtio notifications might be
> expensive. Interpret hypercall return value as a cookie which host can
> use to do device lookups for the next notification more efficiently.
>
> Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
Seems to work fine. (as expected).
Tested-by: Christian Borntraeger <borntrae...@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntrae...@de.ibm.com>
>
> ---
>
> diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
> index 2029b6c..1054f3a 100644
> --- a/drivers/s390/kvm/virtio_ccw.c
> +++ b/drivers/s390/kvm/virtio_ccw.c
> @@ -77,6 +77,7 @@ struct virtio_ccw_vq_info {
> void *queue;
> struct vq_info_block *info_block;
> struct list_head node;
> + long cookie;
> };
>
> #define KVM_VIRTIO_CCW_RING_ALIGN 4096
> @@ -145,15 +146,18 @@ static int ccw_io_helper(struct virtio_ccw_device
> *vcdev,
> }
>
> static inline long do_kvm_notify(struct subchannel_id schid,
> - unsigned long queue_index)
> + unsigned long queue_index,
> + long cookie)
> {
> register unsigned long __nr asm("1") = KVM_S390_VIRTIO_CCW_NOTIFY;
> register struct subchannel_id __schid asm("2") = schid;
> register unsigned long __index asm("3") = queue_index;
> register long __rc asm("2");
> + register long __cookie asm("4") = cookie;
>
> asm volatile ("diag 2,4,0x500\n"
> - : "=d" (__rc) : "d" (__nr), "d" (__schid), "d" (__index)
> + : "=d" (__rc) : "d" (__nr), "d" (__schid), "d" (__index),
> + "d"(__cookie)
> : "memory", "cc");
> return __rc;
> }
> @@ -166,7 +170,7 @@ static void virtio_ccw_kvm_notify(struct virtqueue *vq)
>
> vcdev = to_vc_device(info->vq->vdev);
> ccw_device_get_schid(vcdev->cdev, &schid);
> - do_kvm_notify(schid, virtqueue_get_queue_index(vq));
> + info->cookie = do_kvm_notify(schid, virtqueue_get_queue_index(vq),
> info->cookie);
> }
>
> static int virtio_ccw_read_vq_conf(struct virtio_ccw_device *vcdev,
>
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