Il 30/07/2012 08:25, Wang Sen ha scritto: > 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> Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> -- 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
