RE: [Xen-users] howto build xen from source with existing config?

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: Philippe Trolliet [mailto:p.trolliet@xxxxxxxxxxxxxxx] 
> Sent: 25 May 2007 11:36
> To: Ian Tobin; Petersson, Mats; Xen-Users
> Subject: RE: [Xen-users] howto build xen from source with 
> existing config?
> 
> hi,
> i updated my FC6 and it uses the 2.6.20-xen kernel. so i want 
> to use this version.
> it should be possible to use this kernel and its config in 
> xen 3.1 compile process. i mean, how are the people of redhat 
> doing that?
> they released a newer xen-kernel.
> i´ll just try it like the way you described but with the 
> 2.6.20 config.

The people at redhat (etc) spend many manhours porting the Xen sparse-tree and 
patches to match the new kernel (the sparse-tree contains complete files that 
replace the existing files in the linux-2.6.X-xen tree. So for example, in the 
baremetal version of Linux, there is a bar.c, and in the sparse-tree there is a 
bar-xen.c, which gets copied into the linux-...-xen tree. In the build of the 
linux-xen version, the last part of the build-process will pick the -xen files 
instead of the non-xen version. 

Since the new linux kernel is possibly quite different inside the bar.c, it 
also needs the corresponding changes in the bar-xen.c. Depending on how bar.c 
has changed, this may be rather trivial (add/remove a couple of simple lines, 
change the type of a variable or some such), but it can also be quite 
complicated because the internal workings may have changed. 

It's not just a case of copying the config file, from one version to another, 
it is all the changes in the sparse-tree (or in the linux-2.6.X-xen tree) that 
makes it complex. 

--
Mats
>  
> regards
> philippe
>  
> 
>       -----Original Message-----
>       From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx]On Behalf Of Ian Tobin
>       Sent: Freitag, 25. Mai 2007 12:08
>       To: Petersson, Mats; Philippe Trolliet; Xen-Users
>       Subject: RE: [Xen-users] howto build xen from source 
> with existing config?
>       
>       
>       Hey,
>        
>       dont know if this is any use to you but i found that 
> booting in xen mode and running 
>        
>       make oldconfig
>        
>       in the linux-2.6.18-xen directory
>        
>       seems to import the exiting XEN config into the new 
> one.  Just hold down enter when it prompts for different elements :)
>        
>       thanks
>        
> 
> ________________________________
> 
>       From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx on behalf 
> of Petersson, Mats
>       Sent: Fri 25/05/2007 11:05
>       To: Philippe Trolliet; Xen-Users
>       Subject: RE: [Xen-users] howto build xen from source 
> with existing config?
>       
>       
> 
>       
>       
>       > -----Original Message-----
>       > From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
>       > [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of
>       > Philippe Trolliet
>       > Sent: 25 May 2007 09:09
>       > To: Xen-Users
>       > Subject: [Xen-users] howto build xen from source with 
> existing config?
>       >
>       > hi,
>       > i´m using fedora core 6 and want to build xen 3.1 from source
>       > for the 2.6.20
>       > kernel. how can i build xen with the existing kernel-config
>       > from /boot (e.g.
>       > config-2.6.20-1.2948.fc6xen) and an installed kernel-devel
>       > (source) package?
>       > is it good to use this config or should i create a new one?
>       
>       You should be able to use the config for another 
> kernel, as long as the config is for the same base-level 
> kernel (e.g. it may not work to use a 2.6.18 config to build 
> a 2.6.20 kernel, and probably even worse the other way around).
>       
>       
>       > i searched the net and haven´t found any howto to build xen
>       > from source with
>       > newer kernel versions and existing config files.
>       
>       As stated in a post yesterday, the best way to achieve 
> this is to wait for one of the distributors to do the hard 
> work of figuring out how to adopt the kernel patches from Xen 
> into the next version of the kernel - because that's what 
> you'll have to do.
>       
>       However, if you want to go with the current FC6 Dom0 
> kernel, and use the new 3.1 tools and Xen Hypervisor, that 
> should work ok.
>       
>       --
>       Mats
>       > in the users documentation i found sth like make ARCH=xen
>       > oldconfig but this
>       > doesn´t work. the README couldn´t help me too.
>       > please give detailed instructions.
>       > thank you
>       >
>       > regards
>       > philippe
>       >
>       >
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