From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:42367) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T4V25-0003OT-Ga for qemu-devel@nongnu.org; Thu, 23 Aug 2012 06:53:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1T4V24-0003u1-HQ for qemu-devel@nongnu.org; Thu, 23 Aug 2012 06:53:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39883) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1T4V24-0003tv-8B for qemu-devel@nongnu.org; Thu, 23 Aug 2012 06:53:00 -0400 Message-ID: <50360B80.1080609@redhat.com> Date: Thu, 23 Aug 2012 12:52:48 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1345537427-21601-1-git-send-email-mc@linux.vnet.ibm.com> <50334B51.6050900@redhat.com> <503357B2.5040901@linux.vnet.ibm.com> <50335F78.1030005@redhat.com> <5034BCD1.9020603@linux.vnet.ibm.com> <5034CBF8.3050602@redhat.com> <20120822131348.GA3512@stefanha-thinkpad.localdomain> <5034E918.4030305@redhat.com> <5035F873.6090305@linux.vnet.ibm.com> <5035FFF4.4040603@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/2 v1] blkdrv: Add queue limits parameters for sg block drive List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Stefan Hajnoczi , zwanp@cn.ibm.com, linuxram@us.ibm.com, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, Cong Meng Il 23/08/2012 12:08, Stefan Hajnoczi ha scritto: >> I'm still trying to understand the extent of the problem. >> >> The problem occurs for _USB_ CD-ROMs according to Ben. Passthrough of >> USB storage devices should be done via USB passthrough, not virtio-scsi. >> If we do USB passthrough via the SCSI layer we miss on all the quirks >> that the OS may do based on the USB product/vendor pairs. There's no >> end to these, and some of the quirks may cause the device to lock up or >> corruption. >> >> I'd rather see a reproducer using SAS/ATA/ATAPI disks before punting. > > This issue affects passthrough: either an entire sg device or at least > a SG_IO ioctl (e.g. a non-READ/WRITE SCSI command). > > To reproduce it, check host queue limits and guest virtio-scsi queue > limits. Then pick a command that can exceed the limits and try it > from inside the guest :). Yes, so much is clear. But does it happen _in practice_? Do initiators actually issue commands that are that big? Paolo