On Mon, Jul 30, 2012 at 02:25:06PM +0800, Wang Sen wrote: > 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@xxxxxxxxxxxxxxx> # 3.4: 4fe74b1: [SCSI] virtio-scsi: SCSI driver > Signed-off-by: Wang Sen <senwang@xxxxxxxxxxxxxxxxxx> > --- > drivers/scsi/virtio_scsi.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c > index 1b38431..6661610 100644 > --- a/drivers/scsi/virtio_scsi.c > +++ b/drivers/scsi/virtio_scsi.c > @@ -198,7 +198,7 @@ static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx, > int i; > > for_each_sg(table->sgl, sg_elem, table->nents, i) > - sg_set_buf(&sg[idx++], sg_virt(sg_elem), sg_elem->length); > + sg[idx++] = *sg_elem; > > *p_idx = idx; > } > -- > 1.7.9.5 Paolo has acked and no further issues have been raised. James: Can this be merged? Stefan -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
