Re: [PATCH 2/2] kvm-kmod: Document the build process

[Wolfgang Mauerer <wolfgang.mauerer@siemens.com>]

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Hio,

Dietmar Maurer wrote:
>> +  Before the kvm module can be built, the linux submodule must be
>> initialised
>> +  and populated. The required sequence of commands is
>> +
>> +  git submodule init
>> +  git submodule update
>> +  ./configure
>> +  make sync
>> +  make
>> +
>> +  Notice that you can also specify an existing Linux tree for the
>> +  synchronisation stage by using
>> +
>> +  make sync LINUX=/path/to/tree
> 
> I always get errors when i try to sync (with our Linux-2.6.24 tree)
> 
> ./configure --kerneldir=${TOP}/linux-2.6.24-openvz
> make sync LINUX=${TOP}/linux-2.6.24-openvz
> 
> make[1]: Entering directory `/a/dir/kvm-kmod-2.6.30.1'
> ./sync kvm-kmod-2.6.30.1
> Traceback (most recent call last):
>   File "./sync", line 210, in <module>
>     header_sync(arch)
>   File "./sync", line 181, in header_sync
>     hack(T, 'x86', 'include/linux/kvm.h')
>   File "./sync", line 127, in hack
>     _hack(T + '/' + file, arch)
>   File "./sync", line 118, in _hack
>     data = file(fname).read()
> IOError: [Errno 2] No such file or directory: 'header/include/linux/kvm.h'
> make[1]: *** [sync] Error 1
> 
> Any idea whats wrong?

Do you have a checked out Linux tree in linux-2.6/?
Currently, the linux-2.6 submodule seems to reference
a commit that is not present in the standard kvm
repo, so I assume that git submodule update
has failed for you. For now, you can fix this by
using git checkout in linux-2.6/

Btw.: Wrt. git sync, I've also updated to README
a bit to the two different kernel trees that come into
play. Comments?

Jan: I think the bogous reference is a leftover
from the tree that you've added as submodule; after
my patch to use Avi's tree, the information might be
out of sync.

Best, Wolfgang

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diff --git a/README b/README
index 40a72d3..34cc51a 100644
--- a/README
+++ b/README
@@ -1,16 +1,21 @@
 Building the KVM kernel module is performed differently depending on whether
 you are working from a clone of the git repository or from a source release.
+Notice that two kernels are involved: One from which the KVM sources
+are taken (kernel A), and one for which the module is built (kernel B). 
+For out-of-tree module builds, it is well possible that kernel A is more
+recent than kernel B.
 
 - To build from a release, simply use ./configure (possibly with any
   arguments that are required for your setup, see ./configure --help)
-  and make.
+  and make. The kernel specified with --kerneldir refers to kernel B,
+  that is, the kernel for which the module is built.
 
 - Building from a cloned git repository requires a kernel tree with the main
-  kvm sources that is included as a submodule in the linux-2.6/ directory.  By
-  default, the KVM development tree on git.kernel.org is used, but you can
-  change this setting in .gitmodules
+  kvm sources (kernel A) that is included as a submodule in the linux-2.6/
+  directory.  By default, the KVM development tree on git.kernel.org is used,
+  but you can change this setting in .gitmodules
 
-  Before the kvm module can be built, the linux submodule must be initialised 
+  Before the kvm module can be built, the linux submodule must be initialised
   and populated. The required sequence of commands is
 
   git submodule init
@@ -24,3 +29,5 @@ you are working from a clone of the git repository or from a source release.
 
   make sync LINUX=/path/to/tree
 
+  The synchronisation stage refers to kernel A, that is, the kernel
+  from which the KVM sources are taken.