* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 2:59 ` Gonglei (Arei)
@ 2013-05-24 9:08 ` Stefano Stabellini
2013-05-24 9:08 ` Stefano Stabellini
` (2 subsequent siblings)
3 siblings, 0 replies; 17+ messages in thread
From: Stefano Stabellini @ 2013-05-24 9:08 UTC (permalink / raw)
To: Gonglei (Arei)
Cc: kwolf, Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
xen-devel, Wangzhenguo, afaerber, Huangweidong (Hardware)
[-- Attachment #1: Type: text/plain, Size: 4194 bytes --]
On Fri, 24 May 2013, 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.
I don't think that switching opening flags is the right way to approach
this issue.
Reading back your original email, it seems reasonable to me to return
BSY to the guest.
Probably nobody has seen this problem before because fdatasync is not
usually that slow. I imagine the your bug could be reproduced by
replacing the call to fdatasync with a sleep?
[-- Attachment #2: Type: text/plain, Size: 126 bytes --]
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^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 2:59 ` Gonglei (Arei)
2013-05-24 9:08 ` Stefano Stabellini
@ 2013-05-24 9:08 ` Stefano Stabellini
2013-05-25 7:03 ` Gonglei (Arei)
2013-05-25 7:03 ` Gonglei (Arei)
2013-05-24 12:20 ` Stefan Hajnoczi
2013-05-24 12:20 ` Stefan Hajnoczi
3 siblings, 2 replies; 17+ messages in thread
From: Stefano Stabellini @ 2013-05-24 9:08 UTC (permalink / raw)
To: Gonglei (Arei)
Cc: kwolf, Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
xen-devel, Wangzhenguo, afaerber, Huangweidong (Hardware)
[-- Attachment #1: Type: text/plain, Size: 4194 bytes --]
On Fri, 24 May 2013, 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.
I don't think that switching opening flags is the right way to approach
this issue.
Reading back your original email, it seems reasonable to me to return
BSY to the guest.
Probably nobody has seen this problem before because fdatasync is not
usually that slow. I imagine the your bug could be reproduced by
replacing the call to fdatasync with a sleep?
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 9:08 ` Stefano Stabellini
@ 2013-05-25 7:03 ` Gonglei (Arei)
2013-05-25 7:03 ` Gonglei (Arei)
1 sibling, 0 replies; 17+ messages in thread
From: Gonglei (Arei) @ 2013-05-25 7:03 UTC (permalink / raw)
To: Stefano Stabellini
Cc: kwolf, Hanweidong, Luonengjun, qemu-devel, Wangzhenguo,
xen-devel, afaerber, Huangweidong (Hardware)
> -----Original Message-----
> From: Stefano Stabellini [mailto:stefano.stabellini@eu.citrix.com]
> Sent: Friday, May 24, 2013 5:08 PM
> To: Gonglei (Arei)
> Cc: Stefano Stabellini; xen-devel@lists.xen.org; qemu-devel@nongnu.org;
> Hanweidong; Huangweidong (Hardware); Luonengjun; Wangzhenguo;
> kwolf@redhat.com; afaerber@suse.de
> Subject: RE: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> under xen-4.1.2 and qemu upstream
>
> On Fri, 24 May 2013, 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.
>
> I don't think that switching opening flags is the right way to approach
> this issue.
>
> Reading back your original email, it seems reasonable to me to return
> BSY to the guest.
Perhaps, QEMU comply with the ATA SPEC:
The BSY bit shall be set to one by the device only when one of the following events occurs:
1) after either the negation of RESET- or the setting of the SRST bit to one in the Device
Control register;
2) after writing the Command register if the DRQ bit is not set to one;
3) between blocks of a data transfer during PIO data-in commands before the DRQ bit is
cleared to zero;
4) after the transfer of a data block during PIO data-out commands before the DRQ bit is
cleared to zero;
5) during the data transfer of DMA commands either the BSY bit, the DRQ bit, or both shall
be set to one;
6) after the command packet is received during the execution of a PACKET command.
>
> Probably nobody has seen this problem before because fdatasync is not
> usually that slow. I imagine the your bug could be reproduced by
> replacing the call to fdatasync with a sleep?
Yes, you are right!
-Gonglei
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 9:08 ` Stefano Stabellini
2013-05-25 7:03 ` Gonglei (Arei)
@ 2013-05-25 7:03 ` Gonglei (Arei)
1 sibling, 0 replies; 17+ messages in thread
From: Gonglei (Arei) @ 2013-05-25 7:03 UTC (permalink / raw)
To: Stefano Stabellini
Cc: kwolf, Hanweidong, Luonengjun, qemu-devel, Wangzhenguo,
xen-devel, afaerber, Huangweidong (Hardware)
> -----Original Message-----
> From: Stefano Stabellini [mailto:stefano.stabellini@eu.citrix.com]
> Sent: Friday, May 24, 2013 5:08 PM
> To: Gonglei (Arei)
> Cc: Stefano Stabellini; xen-devel@lists.xen.org; qemu-devel@nongnu.org;
> Hanweidong; Huangweidong (Hardware); Luonengjun; Wangzhenguo;
> kwolf@redhat.com; afaerber@suse.de
> Subject: RE: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> under xen-4.1.2 and qemu upstream
>
> On Fri, 24 May 2013, 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.
>
> I don't think that switching opening flags is the right way to approach
> this issue.
>
> Reading back your original email, it seems reasonable to me to return
> BSY to the guest.
Perhaps, QEMU comply with the ATA SPEC:
The BSY bit shall be set to one by the device only when one of the following events occurs:
1) after either the negation of RESET- or the setting of the SRST bit to one in the Device
Control register;
2) after writing the Command register if the DRQ bit is not set to one;
3) between blocks of a data transfer during PIO data-in commands before the DRQ bit is
cleared to zero;
4) after the transfer of a data block during PIO data-out commands before the DRQ bit is
cleared to zero;
5) during the data transfer of DMA commands either the BSY bit, the DRQ bit, or both shall
be set to one;
6) after the command packet is received during the execution of a PACKET command.
>
> Probably nobody has seen this problem before because fdatasync is not
> usually that slow. I imagine the your bug could be reproduced by
> replacing the call to fdatasync with a sleep?
Yes, you are right!
-Gonglei
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 2:59 ` Gonglei (Arei)
2013-05-24 9:08 ` Stefano Stabellini
2013-05-24 9:08 ` Stefano Stabellini
@ 2013-05-24 12:20 ` Stefan Hajnoczi
2013-05-24 12:20 ` Stefan Hajnoczi
3 siblings, 0 replies; 17+ messages in thread
From: Stefan Hajnoczi @ 2013-05-24 12:20 UTC (permalink / raw)
To: Gonglei (Arei)
Cc: Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
Wangzhenguo, xen-devel, 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/<pid>/maps
or just x <buffer-address> in gdb to see if the buffer is readable.
Stefan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 2:59 ` Gonglei (Arei)
` (2 preceding siblings ...)
2013-05-24 12:20 ` Stefan Hajnoczi
@ 2013-05-24 12:20 ` Stefan Hajnoczi
2013-05-25 7:32 ` Gonglei (Arei)
2013-05-25 7:32 ` Gonglei (Arei)
3 siblings, 2 replies; 17+ messages in thread
From: Stefan Hajnoczi @ 2013-05-24 12:20 UTC (permalink / raw)
To: Gonglei (Arei)
Cc: Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
Wangzhenguo, xen-devel, 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/<pid>/maps
or just x <buffer-address> in gdb to see if the buffer is readable.
Stefan
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 12:20 ` Stefan Hajnoczi
@ 2013-05-25 7:32 ` Gonglei (Arei)
2013-05-25 7:32 ` Gonglei (Arei)
1 sibling, 0 replies; 17+ messages in thread
From: Gonglei (Arei) @ 2013-05-25 7:32 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
Wangzhenguo, xen-devel, Huangweidong (Hardware)
> -----Original Message-----
> From: Stefan Hajnoczi [mailto:stefanha@gmail.com]
> Sent: Friday, May 24, 2013 8:20 PM
> To: Gonglei (Arei)
> Cc: Stefano Stabellini; Hanweidong; Luonengjun; qemu-devel@nongnu.org;
> Wangzhenguo; xen-devel@lists.xen.org; Huangweidong (Hardware)
> Subject: Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> under xen-4.1.2 and qemu upstream
>
> 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.
>
I had tried it, but I got the same error.
> Regarding the EFAULT you are seeing, did you check if the I/O buffer
> address is valid? Try breaking in gdb and inspecting /proc/<pid>/maps
> or just x <buffer-address> in gdb to see if the buffer is readable.
>
> Stefan
Hi, Stefan
The follows are details in gdb:
handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
213 {
(gdb) bt
#0 handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
#1 0x000000000058ba4f in handle_aiocb_rw (aiocb=0x13a0f80) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:254
#2 0x000000000058bde2 in aio_thread (unused=0x0) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:351
#3 0x00007f0a6a1ec7b6 in start_thread () from /lib64/libpthread.so.0
#4 0x00007f0a68f0e9cd in clone () from /lib64/libc.so.6
#5 0x0000000000000000 in ?? ()
(gdb) x 0x7f0a637d7c00
0x7f0a637d7c00: Cannot access memory at address 0x7f0a637d7c00
(gdb) n
214 ssize_t offset = 0;
(gdb)
217 while (offset < aiocb->aio_nbytes) {
(gdb) n
218 if (aiocb->aio_type & QEMU_AIO_WRITE)
(gdb)
224 len = pread(aiocb->aio_fildes,
(gdb)
229 if (len == -1 && errno == EINTR)
(gdb)
231 else if (len == -1) {
(gdb)
232 offset = -errno;
(gdb) p errno
$1 = 14
linux-CGRmYS:~ # cat /proc/21837/maps
00400000-00846000 r-xp 00000000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
00a45000-00a46000 r--p 00445000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
00a46000-00a92000 rw-p 00446000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
00a92000-01344000 rw-p 00000000 00:00 0 [heap]
01344000-01345000 rw-p 00000000 00:00 0 [heap]
01345000-01393000 rw-p 00000000 00:00 0 [heap]
01393000-01394000 rw-p 00000000 00:00 0 [heap]
01394000-013ef000 rw-p 00000000 00:00 0 [heap]
7f0a636d0000-7f0a637d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
7f0a637d0000-7f0a638d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
7f0a638d0000-7f0a639fd000 rw-p 00000000 00:00 0
-Gonglei
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-24 12:20 ` Stefan Hajnoczi
2013-05-25 7:32 ` Gonglei (Arei)
@ 2013-05-25 7:32 ` Gonglei (Arei)
2013-05-27 12:44 ` Stefan Hajnoczi
2013-05-27 12:44 ` [Qemu-devel] " Stefan Hajnoczi
1 sibling, 2 replies; 17+ messages in thread
From: Gonglei (Arei) @ 2013-05-25 7:32 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
Wangzhenguo, xen-devel, Huangweidong (Hardware)
> -----Original Message-----
> From: Stefan Hajnoczi [mailto:stefanha@gmail.com]
> Sent: Friday, May 24, 2013 8:20 PM
> To: Gonglei (Arei)
> Cc: Stefano Stabellini; Hanweidong; Luonengjun; qemu-devel@nongnu.org;
> Wangzhenguo; xen-devel@lists.xen.org; Huangweidong (Hardware)
> Subject: Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> under xen-4.1.2 and qemu upstream
>
> 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.
>
I had tried it, but I got the same error.
> Regarding the EFAULT you are seeing, did you check if the I/O buffer
> address is valid? Try breaking in gdb and inspecting /proc/<pid>/maps
> or just x <buffer-address> in gdb to see if the buffer is readable.
>
> Stefan
Hi, Stefan
The follows are details in gdb:
handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
213 {
(gdb) bt
#0 handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
#1 0x000000000058ba4f in handle_aiocb_rw (aiocb=0x13a0f80) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:254
#2 0x000000000058bde2 in aio_thread (unused=0x0) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:351
#3 0x00007f0a6a1ec7b6 in start_thread () from /lib64/libpthread.so.0
#4 0x00007f0a68f0e9cd in clone () from /lib64/libc.so.6
#5 0x0000000000000000 in ?? ()
(gdb) x 0x7f0a637d7c00
0x7f0a637d7c00: Cannot access memory at address 0x7f0a637d7c00
(gdb) n
214 ssize_t offset = 0;
(gdb)
217 while (offset < aiocb->aio_nbytes) {
(gdb) n
218 if (aiocb->aio_type & QEMU_AIO_WRITE)
(gdb)
224 len = pread(aiocb->aio_fildes,
(gdb)
229 if (len == -1 && errno == EINTR)
(gdb)
231 else if (len == -1) {
(gdb)
232 offset = -errno;
(gdb) p errno
$1 = 14
linux-CGRmYS:~ # cat /proc/21837/maps
00400000-00846000 r-xp 00000000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
00a45000-00a46000 r--p 00445000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
00a46000-00a92000 rw-p 00446000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
00a92000-01344000 rw-p 00000000 00:00 0 [heap]
01344000-01345000 rw-p 00000000 00:00 0 [heap]
01345000-01393000 rw-p 00000000 00:00 0 [heap]
01393000-01394000 rw-p 00000000 00:00 0 [heap]
01394000-013ef000 rw-p 00000000 00:00 0 [heap]
7f0a636d0000-7f0a637d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
7f0a637d0000-7f0a638d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
7f0a638d0000-7f0a639fd000 rw-p 00000000 00:00 0
-Gonglei
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-25 7:32 ` Gonglei (Arei)
@ 2013-05-27 12:44 ` Stefan Hajnoczi
2013-05-28 14:44 ` Konrad Rzeszutek Wilk
2013-05-28 14:44 ` [Qemu-devel] [Xen-devel] " Konrad Rzeszutek Wilk
2013-05-27 12:44 ` [Qemu-devel] " Stefan Hajnoczi
1 sibling, 2 replies; 17+ messages in thread
From: Stefan Hajnoczi @ 2013-05-27 12:44 UTC (permalink / raw)
To: Gonglei (Arei)
Cc: Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
Wangzhenguo, xen-devel, Huangweidong (Hardware)
On Sat, May 25, 2013 at 07:32:55AM +0000, Gonglei (Arei) wrote:
>
>
> > -----Original Message-----
> > From: Stefan Hajnoczi [mailto:stefanha@gmail.com]
> > Sent: Friday, May 24, 2013 8:20 PM
> > To: Gonglei (Arei)
> > Cc: Stefano Stabellini; Hanweidong; Luonengjun; qemu-devel@nongnu.org;
> > Wangzhenguo; xen-devel@lists.xen.org; Huangweidong (Hardware)
> > Subject: Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> > under xen-4.1.2 and qemu upstream
> >
> > 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.
> >
> I had tried it, but I got the same error.
Perhaps that's because the busy bit also needs to be set correctly for
other IDE commands (like read/write requests).
> > Regarding the EFAULT you are seeing, did you check if the I/O buffer
> > address is valid? Try breaking in gdb and inspecting /proc/<pid>/maps
> > or just x <buffer-address> in gdb to see if the buffer is readable.
> >
> > Stefan
>
> Hi, Stefan
>
> The follows are details in gdb:
> handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> 213 {
> (gdb) bt
> #0 handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> #1 0x000000000058ba4f in handle_aiocb_rw (aiocb=0x13a0f80) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:254
> #2 0x000000000058bde2 in aio_thread (unused=0x0) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:351
> #3 0x00007f0a6a1ec7b6 in start_thread () from /lib64/libpthread.so.0
> #4 0x00007f0a68f0e9cd in clone () from /lib64/libc.so.6
> #5 0x0000000000000000 in ?? ()
> (gdb) x 0x7f0a637d7c00
> 0x7f0a637d7c00: Cannot access memory at address 0x7f0a637d7c00
> (gdb) n
> 214 ssize_t offset = 0;
> (gdb)
> 217 while (offset < aiocb->aio_nbytes) {
> (gdb) n
> 218 if (aiocb->aio_type & QEMU_AIO_WRITE)
> (gdb)
> 224 len = pread(aiocb->aio_fildes,
> (gdb)
> 229 if (len == -1 && errno == EINTR)
> (gdb)
> 231 else if (len == -1) {
> (gdb)
> 232 offset = -errno;
> (gdb) p errno
> $1 = 14
>
> linux-CGRmYS:~ # cat /proc/21837/maps
> 00400000-00846000 r-xp 00000000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> 00a45000-00a46000 r--p 00445000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> 00a46000-00a92000 rw-p 00446000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> 00a92000-01344000 rw-p 00000000 00:00 0 [heap]
> 01344000-01345000 rw-p 00000000 00:00 0 [heap]
> 01345000-01393000 rw-p 00000000 00:00 0 [heap]
> 01393000-01394000 rw-p 00000000 00:00 0 [heap]
> 01394000-013ef000 rw-p 00000000 00:00 0 [heap]
> 7f0a636d0000-7f0a637d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
> 7f0a637d0000-7f0a638d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
Interesting, the memory is mapped read/write here. But it's shared
memory that belongs to /proc/xen/privcmd and maybe doesn't support
O_DIRECT?
I don't know the Xen side of things but why are we doing I/O to
/proc/xen/privcmd?
^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-27 12:44 ` Stefan Hajnoczi
@ 2013-05-28 14:44 ` Konrad Rzeszutek Wilk
2013-05-28 14:44 ` [Qemu-devel] [Xen-devel] " Konrad Rzeszutek Wilk
1 sibling, 0 replies; 17+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-05-28 14:44 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Stefano Stabellini, Hanweidong, Luonengjun, qemu-devel,
Wangzhenguo, Gonglei (Arei), xen-devel, Huangweidong (Hardware)
On Mon, May 27, 2013 at 02:44:19PM +0200, Stefan Hajnoczi wrote:
> On Sat, May 25, 2013 at 07:32:55AM +0000, Gonglei (Arei) wrote:
> >
> >
> > > -----Original Message-----
> > > From: Stefan Hajnoczi [mailto:stefanha@gmail.com]
> > > Sent: Friday, May 24, 2013 8:20 PM
> > > To: Gonglei (Arei)
> > > Cc: Stefano Stabellini; Hanweidong; Luonengjun; qemu-devel@nongnu.org;
> > > Wangzhenguo; xen-devel@lists.xen.org; Huangweidong (Hardware)
> > > Subject: Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> > > under xen-4.1.2 and qemu upstream
> > >
> > > 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.
> > >
> > I had tried it, but I got the same error.
>
> Perhaps that's because the busy bit also needs to be set correctly for
> other IDE commands (like read/write requests).
>
> > > Regarding the EFAULT you are seeing, did you check if the I/O buffer
> > > address is valid? Try breaking in gdb and inspecting /proc/<pid>/maps
> > > or just x <buffer-address> in gdb to see if the buffer is readable.
> > >
> > > Stefan
> >
> > Hi, Stefan
> >
> > The follows are details in gdb:
> > handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> > at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> > 213 {
> > (gdb) bt
> > #0 handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> > at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> > #1 0x000000000058ba4f in handle_aiocb_rw (aiocb=0x13a0f80) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:254
> > #2 0x000000000058bde2 in aio_thread (unused=0x0) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:351
> > #3 0x00007f0a6a1ec7b6 in start_thread () from /lib64/libpthread.so.0
> > #4 0x00007f0a68f0e9cd in clone () from /lib64/libc.so.6
> > #5 0x0000000000000000 in ?? ()
> > (gdb) x 0x7f0a637d7c00
> > 0x7f0a637d7c00: Cannot access memory at address 0x7f0a637d7c00
> > (gdb) n
> > 214 ssize_t offset = 0;
> > (gdb)
> > 217 while (offset < aiocb->aio_nbytes) {
> > (gdb) n
> > 218 if (aiocb->aio_type & QEMU_AIO_WRITE)
> > (gdb)
> > 224 len = pread(aiocb->aio_fildes,
> > (gdb)
> > 229 if (len == -1 && errno == EINTR)
> > (gdb)
> > 231 else if (len == -1) {
> > (gdb)
> > 232 offset = -errno;
> > (gdb) p errno
> > $1 = 14
> >
> > linux-CGRmYS:~ # cat /proc/21837/maps
> > 00400000-00846000 r-xp 00000000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> > 00a45000-00a46000 r--p 00445000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> > 00a46000-00a92000 rw-p 00446000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> > 00a92000-01344000 rw-p 00000000 00:00 0 [heap]
> > 01344000-01345000 rw-p 00000000 00:00 0 [heap]
> > 01345000-01393000 rw-p 00000000 00:00 0 [heap]
> > 01393000-01394000 rw-p 00000000 00:00 0 [heap]
> > 01394000-013ef000 rw-p 00000000 00:00 0 [heap]
> > 7f0a636d0000-7f0a637d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
> > 7f0a637d0000-7f0a638d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
>
> Interesting, the memory is mapped read/write here. But it's shared
> memory that belongs to /proc/xen/privcmd and maybe doesn't support
> O_DIRECT?
>
> I don't know the Xen side of things but why are we doing I/O to
> /proc/xen/privcmd?
ioctls are the only things one should be doing on that file.
_______________________________________________
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Xen-devel@lists.xen.org
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^ permalink raw reply [flat|nested] 17+ messages in thread* Re: [Qemu-devel] [Xen-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-27 12:44 ` Stefan Hajnoczi
2013-05-28 14:44 ` Konrad Rzeszutek Wilk
@ 2013-05-28 14:44 ` Konrad Rzeszutek Wilk
1 sibling, 0 replies; 17+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-05-28 14:44 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: Stefano Stabellini, Hanweidong, Luonengjun, qemu-devel,
Wangzhenguo, Gonglei (Arei), xen-devel, Huangweidong (Hardware)
On Mon, May 27, 2013 at 02:44:19PM +0200, Stefan Hajnoczi wrote:
> On Sat, May 25, 2013 at 07:32:55AM +0000, Gonglei (Arei) wrote:
> >
> >
> > > -----Original Message-----
> > > From: Stefan Hajnoczi [mailto:stefanha@gmail.com]
> > > Sent: Friday, May 24, 2013 8:20 PM
> > > To: Gonglei (Arei)
> > > Cc: Stefano Stabellini; Hanweidong; Luonengjun; qemu-devel@nongnu.org;
> > > Wangzhenguo; xen-devel@lists.xen.org; Huangweidong (Hardware)
> > > Subject: Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> > > under xen-4.1.2 and qemu upstream
> > >
> > > 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.
> > >
> > I had tried it, but I got the same error.
>
> Perhaps that's because the busy bit also needs to be set correctly for
> other IDE commands (like read/write requests).
>
> > > Regarding the EFAULT you are seeing, did you check if the I/O buffer
> > > address is valid? Try breaking in gdb and inspecting /proc/<pid>/maps
> > > or just x <buffer-address> in gdb to see if the buffer is readable.
> > >
> > > Stefan
> >
> > Hi, Stefan
> >
> > The follows are details in gdb:
> > handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> > at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> > 213 {
> > (gdb) bt
> > #0 handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> > at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> > #1 0x000000000058ba4f in handle_aiocb_rw (aiocb=0x13a0f80) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:254
> > #2 0x000000000058bde2 in aio_thread (unused=0x0) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:351
> > #3 0x00007f0a6a1ec7b6 in start_thread () from /lib64/libpthread.so.0
> > #4 0x00007f0a68f0e9cd in clone () from /lib64/libc.so.6
> > #5 0x0000000000000000 in ?? ()
> > (gdb) x 0x7f0a637d7c00
> > 0x7f0a637d7c00: Cannot access memory at address 0x7f0a637d7c00
> > (gdb) n
> > 214 ssize_t offset = 0;
> > (gdb)
> > 217 while (offset < aiocb->aio_nbytes) {
> > (gdb) n
> > 218 if (aiocb->aio_type & QEMU_AIO_WRITE)
> > (gdb)
> > 224 len = pread(aiocb->aio_fildes,
> > (gdb)
> > 229 if (len == -1 && errno == EINTR)
> > (gdb)
> > 231 else if (len == -1) {
> > (gdb)
> > 232 offset = -errno;
> > (gdb) p errno
> > $1 = 14
> >
> > linux-CGRmYS:~ # cat /proc/21837/maps
> > 00400000-00846000 r-xp 00000000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> > 00a45000-00a46000 r--p 00445000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> > 00a46000-00a92000 rw-p 00446000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> > 00a92000-01344000 rw-p 00000000 00:00 0 [heap]
> > 01344000-01345000 rw-p 00000000 00:00 0 [heap]
> > 01345000-01393000 rw-p 00000000 00:00 0 [heap]
> > 01393000-01394000 rw-p 00000000 00:00 0 [heap]
> > 01394000-013ef000 rw-p 00000000 00:00 0 [heap]
> > 7f0a636d0000-7f0a637d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
> > 7f0a637d0000-7f0a638d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
>
> Interesting, the memory is mapped read/write here. But it's shared
> memory that belongs to /proc/xen/privcmd and maybe doesn't support
> O_DIRECT?
>
> I don't know the Xen side of things but why are we doing I/O to
> /proc/xen/privcmd?
ioctls are the only things one should be doing on that file.
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed under xen-4.1.2 and qemu upstream
2013-05-25 7:32 ` Gonglei (Arei)
2013-05-27 12:44 ` Stefan Hajnoczi
@ 2013-05-27 12:44 ` Stefan Hajnoczi
1 sibling, 0 replies; 17+ messages in thread
From: Stefan Hajnoczi @ 2013-05-27 12:44 UTC (permalink / raw)
To: Gonglei (Arei)
Cc: Hanweidong, Stefano Stabellini, Luonengjun, qemu-devel,
Wangzhenguo, xen-devel, Huangweidong (Hardware)
On Sat, May 25, 2013 at 07:32:55AM +0000, Gonglei (Arei) wrote:
>
>
> > -----Original Message-----
> > From: Stefan Hajnoczi [mailto:stefanha@gmail.com]
> > Sent: Friday, May 24, 2013 8:20 PM
> > To: Gonglei (Arei)
> > Cc: Stefano Stabellini; Hanweidong; Luonengjun; qemu-devel@nongnu.org;
> > Wangzhenguo; xen-devel@lists.xen.org; Huangweidong (Hardware)
> > Subject: Re: [Qemu-devel] use O_DIRECT to open disk images for IDE failed
> > under xen-4.1.2 and qemu upstream
> >
> > 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.
> >
> I had tried it, but I got the same error.
Perhaps that's because the busy bit also needs to be set correctly for
other IDE commands (like read/write requests).
> > Regarding the EFAULT you are seeing, did you check if the I/O buffer
> > address is valid? Try breaking in gdb and inspecting /proc/<pid>/maps
> > or just x <buffer-address> in gdb to see if the buffer is readable.
> >
> > Stefan
>
> Hi, Stefan
>
> The follows are details in gdb:
> handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> 213 {
> (gdb) bt
> #0 handle_aiocb_rw_linear (aiocb=0x13a0f80, buf=0x7f0a637d7c00 <Address 0x7f0a637d7c00 out of bounds>)
> at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:213
> #1 0x000000000058ba4f in handle_aiocb_rw (aiocb=0x13a0f80) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:254
> #2 0x000000000058bde2 in aio_thread (unused=0x0) at /mnt/sdd/gonglei/xen-4.1.2/tools/qemu-xen/posix-aio-compat.c:351
> #3 0x00007f0a6a1ec7b6 in start_thread () from /lib64/libpthread.so.0
> #4 0x00007f0a68f0e9cd in clone () from /lib64/libc.so.6
> #5 0x0000000000000000 in ?? ()
> (gdb) x 0x7f0a637d7c00
> 0x7f0a637d7c00: Cannot access memory at address 0x7f0a637d7c00
> (gdb) n
> 214 ssize_t offset = 0;
> (gdb)
> 217 while (offset < aiocb->aio_nbytes) {
> (gdb) n
> 218 if (aiocb->aio_type & QEMU_AIO_WRITE)
> (gdb)
> 224 len = pread(aiocb->aio_fildes,
> (gdb)
> 229 if (len == -1 && errno == EINTR)
> (gdb)
> 231 else if (len == -1) {
> (gdb)
> 232 offset = -errno;
> (gdb) p errno
> $1 = 14
>
> linux-CGRmYS:~ # cat /proc/21837/maps
> 00400000-00846000 r-xp 00000000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> 00a45000-00a46000 r--p 00445000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> 00a46000-00a92000 rw-p 00446000 08:05 28601 /usr/lib/xen/bin/qemu-system-i386
> 00a92000-01344000 rw-p 00000000 00:00 0 [heap]
> 01344000-01345000 rw-p 00000000 00:00 0 [heap]
> 01345000-01393000 rw-p 00000000 00:00 0 [heap]
> 01393000-01394000 rw-p 00000000 00:00 0 [heap]
> 01394000-013ef000 rw-p 00000000 00:00 0 [heap]
> 7f0a636d0000-7f0a637d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
> 7f0a637d0000-7f0a638d0000 rw-s 00000000 00:03 4026532176 /proc/xen/privcmd
Interesting, the memory is mapped read/write here. But it's shared
memory that belongs to /proc/xen/privcmd and maybe doesn't support
O_DIRECT?
I don't know the Xen side of things but why are we doing I/O to
/proc/xen/privcmd?
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