2012/7/25 Boaz Harrosh <bharrosh@xxxxxxxxxxx>: > On 07/25/2012 02:44 PM, Sen Wang wrote: > >> 2012/7/25 Paolo Bonzini <pbonzini@xxxxxxxxxx>: >>> Il 25/07/2012 10:29, 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 there are some HighMem pages in >>>> table->sgl 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. >>> >>> Heh, I was compiling (almost) the same patch as we speak. :) >> >> Uh, what a coincidence! :) >> >>> >>> I've never seen QEMU crash; the VM would more likely just fail to boot >>> with a panic. But it's the same bug anyway. >> >> I never met this before. How this situation happens? >> >>> >>>> My solution is using sg_set_page instead of sg_set_buf. >>>> >>>> I have tested the patch on my workstation. QEMU would not crash any more. >>>> >>>> Signed-off-by: Wang Sen <senwang@xxxxxxxxxxxxxxxxxx> >>>> --- >>>> drivers/scsi/virtio_scsi.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c >>>> index 1b38431..fc5c88a 100644 >>>> --- a/drivers/scsi/virtio_scsi.c >>>> +++ b/drivers/scsi/virtio_scsi.c >>>> @@ -198,7 +198,8 @@ 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_set_page(&sg[idx++], sg_page(sg_elem), sg_elem->length, >>>> + sg_elem->offset); >>> >>> This can simply be >>> >>> sg[idx++] = *sg_elem; >>> >> >> Yes, I saw your another E-mail. I think you're right. Simply calling >> sg_set_page can not handle >> the flag bits correctly. So, I'll repost the patch soon. Thank you! >> > > > No this code is correct, though you will need to make sure to properly > terminate the destination sg_list. Yes, the terminate marker in the destination list is set when initialization. sg_set_page would not break this marker because it saved both the two maker bits at sg_asign_page. Also, the allocation of destination sg list considered the total number of the source sg_list. So, sg_set_page can work correctly. The value assignment method also can also work correctly, because the termination marker in source sg_list has been set in blk_rq_map_sg(), as the last entry of source sg_list is just copied to the the last entry in destination list. Uh, Paolo, Boaz, have you reached agreement on which method to use? > > But since old code was using sg_set_buf(), than it means it was properly > terminated before, and there for this code is good as is please don't > touch it. > > Thanks > Boaz > >>> Can you repost it with this change, and also add stable@xxxxxxxxxxxxxxx >>> to the Cc? Thanks very much! >>> >>> Paolo >>> -- >>> 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 >> >> >> > -- ------------------------------------------ Wang Sen Addr: XUPT,Xi'an,Shaanxi,China Email: kelvin.xupt@xxxxxxxxx ------------------------------------------ -- 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
