Keep a separate lock for each virtqueue.  While not particularly
important now, it prepares the code for when we will add support
for multiple request queues.  It is also more tidy as soon as
we introduce a separate lock for the sglist.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

Separate virtqueue_kick_prepare from virtqueue_notify, so that the
expensive vmexit is done without holding the lock.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

Fix a use-after-free in the TMF path, where cmd may have been already
freed by virtscsi_complete_free when wait_for_completion restarts
executing virtscsi_tmf.  Technically a race, but in practice the command
will always be freed long before the completion waiter is awoken.

The fix is to make callers specifying a completion responsible for
freeing the command in all cases.
Signed-off-by: NHu Tao <hutao@cn.fujitsu.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>

The virtio-scsi HBA is the basis of an alternative storage stack
for QEMU-based virtual machines (including KVM).  Compared to
virtio-blk it is more scalable, because it supports many LUNs
on a single PCI slot), more powerful (it more easily supports
passthrough of host devices to the guest) and more easily
extensible (new SCSI features implemented by QEMU should not
require updating the driver in the guest).
Acked-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>