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

[Michal Novotny <minovotn@redhat.com>]

On 06/04/2010 12:42 PM, Pasi Kärkkäinen wrote:
> 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?
>    

It's the one that's being automatically downloaded from git as 
linux-2.6-pvops.git. The URL is 
git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git with the 
"fetch" being set to "+refs/heads/*:refs/remotes/xen/*". This is the 
.git/config automatically created by `make world` in xen-unstable tree:

[core]
         repositoryformatversion = 0
         filemode = true
         bare = false
         logallrefupdates = true
[remote "xen"]
         url = git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git
         fetch = +refs/heads/*:refs/remotes/xen/*
[branch "xen/stable-2.6.31.x"]
         remote = xen
         merge = refs/heads/xen/stable-2.6.31.x

By default it's using uhci-hcd/ehci-hcd and ohci-hcd as builtins but I 
needed to change it to be modules since otherwise it's being stuck. I'm 
trying this on RHEL-5 dom0 (I'm having second partition RHEL-5 with 
upstream xen).
> See my example .config files from:
> http://wiki.xensource.com/xenwiki/XenParavirtOps in the "troubleshooting" section.
>    

I'll have a look, thanks for the link.

> 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
>    

Oh, ok, this may be very useful since I'm trying this on RHEL-5. Thanks!

> 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.
>
>    

Great! Thanks for your help Pasi! If anything I'll let you know.

Michal

> -- 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@redhat.com>
>>>>
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@lists.xensource.com
>>>> http://lists.xensource.com/xen-devel
>>>>          
>>>
>>>        
>>
>> -- 
>> Michal Novotny<minovotn@redhat.com>, RHCE
>> Virtualization Team (xen userspace), Red Hat
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
>>      


-- 
Michal Novotny<minovotn@redhat.com>, RHCE
Virtualization Team (xen userspace), Red Hat