[PATCH v4 1/6] virtio_ccw: pass a cookie value to kvm hypercall

Cornelia Huck
2013-02-28T09:22:40Z

From: "Michael S. Tsirkin" <mst@redhat.com>

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.

[CH: Fix line > 80 chars]
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
drivers/s390/kvm/virtio_ccw.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 3217dfe..259a2fb 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 +170,8 @@ 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,
--
1.7.12.4