Re: [Xen-devel] [PATCH] qemu-xen-3.4-testing: Fix read-only image file handling

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Fri, Jun 04, 2010 at 11:37:51AM +0200, Michal Novotny wrote:
> Oh, one more thing I've discovered now. Since the codebase for  
> qemu-xen-unstable is looking the same like for qemu-xen-3.4-testing and  
> the patch is applicable without any modifications it could be working  
> for xen-4.1 unstable as well, unfortunately I was not able to boot PVOPS  
> kernel since it always ends up in kernel panic, maybe the missing  
> drivers or something like that.
>

What kernel version? Did you use xen/stable-2.6.32.x branch from xen.git? 

See my example .config files from:
http://wiki.xensource.com/xenwiki/XenParavirtOps in the "troubleshooting" 
section.

Works on F12/F13 dom0's. 

For el5 dom0 you might need these:
http://wiki.xensource.com/xenwiki/2.6.18-to-2.6.31-and-higher

aka
CONFIG_SYSFS_DEPRECATED=y
CONFIG_SYSFS_DEPRECATED_V2=y

Also atm I think you need CONFIG_XEN_XENBUS_FRONTEND=y in the .config
because of the recently added pv-on-hvm drivers (you'll get build failure 
without that option),
so you need XEN_PCIDEV_FRONTEND XEN_BLKDEV_FRONTEND or XEN_NETDEV_FRONTEND or 
XEN_FBDEV_FRONTEND needs to be =y.

-- Pasi


> On 06/03/2010 04:12 PM, Michal Novotny wrote:
>> Oh, just one more thing that should be mentioned:
>>
>> When you want to mount an image that is set as read-only in the domain  
>> configuration file but you omit to set mode to read-only it results  
>> into I/O errors when processing the requests. Remounting as read-only  
>> or unmounting and remounting using the `mount /dev/* /path/to/mount -o  
>> ro` shall do the mounting the correct way, i.e. with no I/O errors, so  
>> make sure you mount those disks as read-only otherwise you can be  
>> getting errors like:
>>
>> end_request: I/O error, dev hdb, sector 52
>>
>> Buffer I/O error on device hdb1, logical block 1
>>
>> lost page write due to I/O error on hdb1
>>
>>
>> and for IDE devices you'll be getting several additional DeviceFault  
>> errors since mounting the device read-write (default setting) writes  
>> some data onto a disk at the mount-time.
>>
>> Michal
>>
>> On 06/03/2010 04:04 PM, Michal Novotny wrote:
>>> [Well, I did send an e-mail to the list using git but it's not here  
>>> so I'm forwarding the e-mail to the list for sure:]
>>>
>>> Hi,
>>> this is the patch for qemu-xen-3.4-testing to fix the read-only
>>> image file handling since the image file was always treated as
>>> read-write which means that all the HVM guests were able to
>>> write to all the disk images available in domain configuration
>>> file no matter what the mode of the image was defined. This
>>> patch fixes this functionality to honor the O_RDONLY in the
>>> BDRV_O_ACCESS flag in block.c and also fixes the IDE and SCSI
>>> interfaces that uses it.
>>>
>>> It's been tested on RHEL-5 with xen-3.4-testing version of
>>> upstream xen with xen-3.4-testing qemu implementation.
>>>
>>> For SCSI devices the DATA PROTECT request sense has been added
>>> as found at: http://en.wikipedia.org/wiki/SCSI_Request_Sense_Command
>>>
>>> file no matter what the mode of the image was defined. This
>>> patch fixes this functionality to honor the O_RDONLY in the
>>> BDRV_O_ACCESS flag in block.c and also fixes the IDE and SCSI
>>> interfaces that uses it.
>>>
>>> It's been tested on RHEL-5 with xen-3.4-testing version of
>>> Michal
>>>
>>> Signed-off-by: Michal Novotny <minovotn@xxxxxxxxxx>
>>>
>>>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>> http://lists.xensource.com/xen-devel
>>
>>
>
>
> -- 
> Michal Novotny<minovotn@xxxxxxxxxx>, RHCE
> Virtualization Team (xen userspace), Red Hat
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

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