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KVM: s390: Gracefully handle busy conditions on ccw_device_start 

In rare cases a virtio command might try to issue a ccw before a former
ccw was answered with a tsch. This will cause CC=2 (busy). Lets just
retry in that case.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Christian Borntraeger 2013-01-07 15:51:52 +01:00 committed by Marcelo Tosatti
parent 73fa21ea4f
commit b26ba22bb4
1 changed files with 8 additions and 5 deletions
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13
drivers/s390/kvm/virtio_ccw.c
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@ -132,11 +132,14 @@ static int ccw_io_helper(struct virtio_ccw_device *vcdev,
unsigned long flags;
int flag = intparm & VIRTIO_CCW_INTPARM_MASK;
spin_lock_irqsave(get_ccwdev_lock(vcdev->cdev), flags);
ret = ccw_device_start(vcdev->cdev, ccw, intparm, 0, 0);
if (!ret)
vcdev->curr_io |= flag;
spin_unlock_irqrestore(get_ccwdev_lock(vcdev->cdev), flags);
do {
spin_lock_irqsave(get_ccwdev_lock(vcdev->cdev), flags);
ret = ccw_device_start(vcdev->cdev, ccw, intparm, 0, 0);
if (!ret)
vcdev->curr_io |= flag;
spin_unlock_irqrestore(get_ccwdev_lock(vcdev->cdev), flags);
cpu_relax();
} while (ret == -EBUSY);
wait_event(vcdev->wait_q, doing_io(vcdev, flag) == 0);
return ret ? ret : vcdev->err;
}