From: Christian Borntraeger <borntraeger@de.ibm.com>
Date: Mon, 7 Jan 2013 14:51:52 +0000 (+0100)
Subject: KVM: s390: Gracefully handle busy conditions on ccw_device_start
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=b26ba22bb4f12289f9d5eb878c490e674934a197;p=openwrt%2Fstaging%2Fblogic.git

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>
---

diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 70419a75d0e0..2edd94af131c 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -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;
 }