When using the commands below to write some data to a virtio-scsi LUN of the
QEMU guest(32-bit) with 1G physical memory(qemu -m 1024), the qemu will crash.
# sudo mkfs.ext4 /dev/sdb (/dev/sdb is the virtio-scsi LUN.)
# sudo mount /dev/sdb /mnt
# dd if=/dev/zero of=/mnt/file bs=1M count=1024
In current implementation, sg_set_buf is called to add buffers to sg list which
is put into the virtqueue eventually. But if there are some HighMem pages in
table->sgl you can not get virtual address by sg_virt. So, sg_virt(sg_elem) may
return NULL value. This will cause QEMU exit when virtqueue_map_sg is called
in QEMU because an invalid GPA is passed by virtqueue.
Two solutions are discussed here:
http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/00675.html
Finally, value assignment approach was adopted because:
Value assignment creates a well-formed scatterlist, because the termination
marker in source sg_list has been set in blk_rq_map_sg(). The last entry of the
source sg_list is just copied to the the last entry in destination list. Note
that, for now, virtio_ring does not care about the form of the scatterlist and
simply processes the first out_num + in_num consecutive elements of the sg[]
array.
I have tested the patch on my workstation. QEMU would not crash any more.
Cc: <stable@vger.kernel.org> # 3.4: 4fe74b1: [SCSI] virtio-scsi: SCSI driver
Signed-off-by: Wang Sen <senwang@linux.vnet.ibm.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This patch changes virtio-scsi to use a new virtio_driver->scan() callback
so that scsi_scan_host() can be properly invoked once virtio_dev_probe() has
set add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK) to signal active virtio-ring
operation, instead of from within virtscsi_probe().
This fixes a bug where SCSI LUN scanning for both virtio-scsi-raw and
virtio-scsi/tcm_vhost setups was happening before VIRTIO_CONFIG_S_DRIVER_OK
had been set, causing VIRTIO_SCSI_S_BAD_TARGET to occur. This fixes a bug
with virtio-scsi/tcm_vhost where LUN scan was not detecting LUNs.
Tested with virtio-scsi-raw + virtio-scsi/tcm_vhost w/ IBLOCK on 3.5-rc2 code.
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This patch implements the hotplug support for virtio-scsi.
When there is a device attached/detached, the virtio-scsi driver will be
signaled via event virtual queue and it will add/remove the scsi device
in question automatically.
Signed-off-by: Sen Wang <senwang@linux.vnet.ibm.com>
Signed-off-by: Cong Meng <mc@linux.vnet.ibm.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
To improve performance for I/O to different targets, add a separate
scatterlist for each of them.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
We do not need the sglist after calling virtqueue_add_buf. Hence we
can "pipeline" the locked operations and start preparing the sglist
for the next request while we kick the virtqueue.
Together with the previous two patches, this improves performance as
follows. For a simple "if=/dev/sda of=/dev/null bs=128M iflag=direct"
(the source being a 10G disk, residing entirely in the host buffer cache),
the additional locking does not cause any penalty with only one dd
process, but 2 simultaneous I/O operations improve their times by 3%:
number of simultaneous dd
1 2
----------------------------------------
current 5.9958s 10.2640s
patched 5.9531s 9.8663s
(Times are best of 10).
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James 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: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James 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: Hu Tao <hutao@cn.fujitsu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James 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: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
