From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:36770) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ufqyk-0004d9-I7 for qemu-devel@nongnu.org; Fri, 24 May 2013 08:20:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ufqyb-0005xn-QN for qemu-devel@nongnu.org; Fri, 24 May 2013 08:20:14 -0400 Received: from mail-we0-x231.google.com ([2a00:1450:400c:c03::231]:38895) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ufqyb-0005vl-H5 for qemu-devel@nongnu.org; Fri, 24 May 2013 08:20:05 -0400 Received: by mail-we0-f177.google.com with SMTP id n57so2766718wev.22 for ; Fri, 24 May 2013 05:20:04 -0700 (PDT) Date: Fri, 24 May 2013 14:20:01 +0200 From: Stefan Hajnoczi Message-ID: <20130524122001.GC23160@stefanha-thinkpad.redhat.com> References: <33183CC9F5247A488A2544077AF190206C8FCB9B@szxeml538-mbx.china.huawei.com> <33183CC9F5247A488A2544077AF190206C8FFCF4@szxeml538-mbx.china.huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <33183CC9F5247A488A2544077AF190206C8FFCF4@szxeml538-mbx.china.huawei.com> Subject: Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Gonglei (Arei)" Cc: Hanweidong , Stefano Stabellini , Luonengjun , "qemu-devel@nongnu.org" , Wangzhenguo , "xen-devel@lists.xen.org" , "Huangweidong (Hardware)" On Fri, May 24, 2013 at 02:59:05AM +0000, Gonglei (Arei) wrote: > Hi, > > > > > On Thu, 23 May 2013, Gonglei (Arei) wrote: > > > Hi, all > > > > > > I use O_DIRECT to open disk images for IDE, but I'm failed. After debug, I get > > the below logs: > > > [2013-05-22 23:25:46] ide: CMD=c8 > > > [2013-05-22 23:25:46] bmdma: readb 0x00 : 0x08 > > > [2013-05-22 23:25:46] bmdma: writeb 0x00 : 0x09 > > > [2013-05-22 23:25:46] bmdma_cmd_writeb: 0x00000009 > > > [2013-05-22 23:25:46] bmdma: readb 0x02 : 0x01 > > > [2013-05-22 23:25:46] bmdma: readb 0x02 : 0x01 > > > [2013-05-22 23:25:46] bmdma: readb 0x02 : 0x01 > > > [2013-05-22 23:25:46] bmdma: readb 0x02 : 0x01 > > > [2013-05-22 23:25:46] bmdma: readb 0x02 : 0x01 > > > [2013-05-22 23:25:46] bmdma: readb 0x02 : 0x01 > > > [2013-05-22 23:26:39] bmdma: writeb 0x00 : 0x08 > > > [2013-05-22 23:26:39] bmdma_cmd_writeb: 0x00000008 > > > [2013-05-22 23:26:56] ====== offset:0 buf:0x7ff100f21c00 count:512 > > aio_offset:0 > > > [2013-05-22 23:31:30] ====== offset:0 buf:0x7ff100f21c00 count:512 > > aio_offset:0 > > > [2013-05-22 23:31:30] ====== handle_aiocb_rw_linear errno: -14 > > > [2013-05-22 23:31:30] ====== paio_complete errno=14 > > > [2013-05-22 23:31:30] ====== ide_dma_error!!! > > > [2013-05-22 23:31:30] ide: read status addr=0x3f6 val=41 > > > > > > QEMU command line : > > > qemu-system-i386 -xen-domid 837 -chardev > > socket,id=libxl-cmd,path=/var/run/xen/qmp-libxl-837,server,nowait -mon > > chardev=libxl-cmd,mode=control -name suse11 -vnc 0.0.0.0:1 -serial pty -boot > > order=c -usb -usbdevice tablet -smp 2,maxcpus=2 -device > > rtl8139,id=nic0,netdev=net0,mac=00:16:3e:13:d3:72 -netdev > > type=tap,id=net0,ifname=tap837.0,downscript=no -M xenfv -m 2040 -drive > > file=/mnt/sdd/image/suse.image,if=ide,index=0,media=disk,format=raw,cache > > =none > > > > > > errno 14 shows Bad Address. And I find QEMU_AIO_MISALIGNED flag bit is > > not set through debug. > > > > > > /* > > > * If O_DIRECT is used the buffer needs to be aligned on a sector > > > * boundary. Check if this is the case or tell the low-level > > > * driver that it needs to copy the buffer. > > > */ > > > if ((bs->open_flags & BDRV_O_NOCACHE)) { > > > if (!bdrv_qiov_is_aligned(bs, qiov)) { //if the address is > > aligned-512, will no meet the conditions > > > type |= QEMU_AIO_MISALIGNED; > > > #ifdef CONFIG_LINUX_AIO > > > } else if (s->use_aio) { > > > return laio_submit(bs, s->aio_ctx, s->fd, sector_num, qiov, > > > nb_sectors, cb, opaque, type); > > > #endif > > > > > > Next process: > > > static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb) > > > { > > > ssize_t nbytes; > > > char *buf; > > > > > > if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) { > > > /* > > > * If there is just a single buffer, and it is properly aligned > > > * we can just use plain pread/pwrite without any problems. > > > */ > > > if (aiocb->aio_niov == 1) > > > return handle_aiocb_rw_linear(aiocb, > > aiocb->aio_iov->iov_base); //this way, and reports errno 14 next > > > > > > Anyone have a good method to resolve this bug? Thanks! > > > > I know that this is not the answer you are looking for but why do you > > want to use O_DIRECT with IDE? > > It should be perfectly safe to use write-back. > > A few days ago, I asked a question about the IDE FLUSH time of guest： > http://lists.nongnu.org/archive/html/qemu-devel/2013-05/msg02642.html > > finally I found that because Qemu use write-back flag to open disk images by default. > so I hope to use O_DIRECT to avoid meeting that problem, but I'm failed under Xen platform with Qemu upstream. cache=none does not eliminate the need for flush. If you want to do that, try cache=writethrough or cache=directsync. Regarding the EFAULT you are seeing, did you check if the I/O buffer address is valid? Try breaking in gdb and inspecting /proc//maps or just x in gdb to see if the buffer is readable. Stefan