On 07/25/2012 11:44 AM, Paolo Bonzini wrote: > 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. :) > > 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. > >> 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 <senw...@linux.vnet.ibm.com> >> --- >> 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; > > Can you repost it with this change, and also add sta...@vger.kernel.org > to the Cc? Thanks very much! >
No! Please use sg_set_page()! Look at sg_set_page(), which calls sg_assign_page(). It has all these jump over chained arrays. When you'll start using long sg_lists (which you should) then jumping from chain to chain must go through sg_page(sg_elem) && sg_assign_page(), As in the original patch. Thanks Boaz > Paolo > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
