From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wang Sen Subject: [PATCH v3] scsi: virtio-scsi: Fix address translation failure of HighMem pages used by sg list Date: Mon, 30 Jul 2012 14:25:06 +0800 Message-ID: <1343629506-29627-1-git-send-email-senwang@linux.vnet.ibm.com> Return-path: Received: from e28smtp03.in.ibm.com ([122.248.162.3]:48512 "EHLO e28smtp03.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751529Ab2G3G0e (ORCPT ); Mon, 30 Jul 2012 02:26:34 -0400 Received: from /spool/local by e28smtp03.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 30 Jul 2012 11:56:31 +0530 Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: JBottomley@parallels.com, pbonzini@redhat.com, bharrosh@panasas.com, stefanha@linux.vnet.ibm.com Cc: mc@linux.vnet.ibm.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, zwanp@cn.ibm.com, xiaoguangrong@linux.vnet.ibm.com, Wang Sen 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: # 3.4: 4fe74b1: [SCSI] virtio-scsi: SCSI driver Signed-off-by: Wang Sen --- 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