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Date: Mon, 30 Jul 2012 09:45:33 +0200 From: Paolo Bonzini <pbonzini@...hat.com> To: Wang Sen <senwang@...ux.vnet.ibm.com> CC: JBottomley@...allels.com, bharrosh@...asas.com, stefanha@...ux.vnet.ibm.com, mc@...ux.vnet.ibm.com, linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org, zwanp@...ibm.com, xiaoguangrong@...ux.vnet.ibm.com Subject: Re: [PATCH v3] scsi: virtio-scsi: Fix address translation failure of HighMem pages used by sg list 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@...r.kernel.org> # 3.4: 4fe74b1: [SCSI] virtio-scsi: SCSI driver > Signed-off-by: Wang Sen <senwang@...ux.vnet.ibm.com> Acked-by: Paolo Bonzini <pbonzini@...hat.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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