Re: [PATCH] Make KVM compile on split source/object kernel configurations

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Am 18.09.2008 um 04:12 schrieb "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>:

Alexander Graf wrote:
On Sep 16, 2008, at 12:22 PM, Zhang, Xiantao wrote:

Alexander Graf wrote:
On Sep 16, 2008, at 9:22 AM, Zhang, Xiantao wrote:

Alexander Graf wrote:
KVM as is assumes that the kernel obj dir and the kernel source
dir are at the same location. This is true for most self-built
vanilla kernels, but some distributions split these up (e.g.
SUSE).
To keep compatible and have users have a good experience on
building KVM on any distribution, this patch attempts to rebuild
the logic from the kernel Makefile as closely as possible. With
it I successfully built KVM on a current SUSE system.

Signed-off-by: Alexander Graf <agraf@xxxxxxx>

Please check and see if it breaks the build process for anyone
else. Building with IA64 on SUSE-kernels is still broken due to
similar but separate problems.

Hi, Graf
   what problems did you meet when building kvm/ia64 ?
Xiantao


This is the list of stuff I had to modify to get kvm-74 to run. I
haven't tried anything more recent yet.

1) -mno-sdata does not work. Qemu CFLAGS need to be -msdata

Which version of GCC are you using ?

# gcc --version
gcc (SUSE Linux) 4.3.2 20080815 (prerelease) [gcc-4_3-branch revision
139129]



2) In qemu/ia64.ld SEARCH_DIR is invalid for SUSE. It shouldn't
search in /usr/ia64-linux but in /usr/ia64-suse-linux.
You can make a patch to fix it.

Right, this one should be really easy to fix.

3) TARGET_PAGE_BITS is wrong
Currently, we just set TARGET_PAGE_BITS to 16 by hardcoding in Qemu.
In the future, we should add the logic to make it equal to kernel's
PAGE_SHIFT.

From what I read on the KVM IA64 ML, this is not the first time
someone ran into this issue. Sounds like a really good idea to add the
logic ;-).

4) kernel/ia64/Makefile.pre assumes to find .S files in $KERNELDIR.
They are in $SOURCEDIR.

There is no issue here, I think.  You have to set corrent $KERNELDIR
through ./configure --kerneldir=xxxx once target machine and build
machine is not same.

No, since $KERNELDIR is the build dir, as that one contains all the
configurations. The source dir only contains the sources.

5) kernel/ia64/Makefile.pre suffers from the same problem my
original fix for x86 addressed.

Ditto.

6) The IA64 kernel build system is broken. The file asm-ia64/nr-
irqs.h gets generated during the kernel build, but is not exported
as obj, so it won't be in the split obj directory. Since the
source-dir is clean though, the file simply does not exist on SUSE
rpms.

You mean the source-dir is clean ?  So the generated header files
including (linux/autoconf.h, asm-offsets.h...)should be removed
wholely? I don't think they can be built with a clean source for
most modules.

This is what I'm talking about all the time :-). For SUSE kernels
there are two distinct directories:

# ls -l /usr/src
drwxr-xr-x 24 root root 4096 Aug 27 14:51 linux-2.6.27-rc4-
HEAD_20080825213702
drwxr-xr-x  3 root root 4096 Aug 25 23:28 linux-2.6.27-rc4-
HEAD_20080825213702-obj

whereas the normal directory contains the sources and the -obj
directory contains all files that were generated during the build.
Scratch that with the 2 rpm files - they are all in kernel-sources.

# ls -l
/usr/src/linux-2.6.27-rc4-HEAD_20080825213702-obj/ia64/default/ total
568
-rw-r--r-- 1 root root  76287 Aug 25 23:27 .config
-rw-r--r-- 2 root root    554 Aug 25 23:28 Makefile
-rw-r--r-- 1 root root 468615 Aug 25 23:51 Module.symvers
drwxr-xr-x 3 root root   4096 Aug 26 18:01 arch
drwxr-xr-x 5 root root   4096 Aug 26 18:01 include
drwxr-xr-x 2 root root   4096 Aug 26 18:01 include2
drwxr-xr-x 2 root root   4096 Aug 25 23:28 kernel
drwxr-xr-x 6 root root   4096 Aug 26 18:01 scripts

The problem is now that a lot of people assume these two directories
to be one. This is the default mode when you compile a kernel. SUSE
does not take this route though, and hasn't for quite a while now. I
don't know about other distributions, but I guess we're not the only
ones ;-).
Okay, I see now. But due to shortage of Suse OS at hand, I can't try it . Anyway once you found any issues related to the compability with Suse
OS, welcome to post patches to fix them. :)

Oh I will :). I just wanted to make sure x86 compiles for everyone first, as that probably hurts more users :).

Thanks for caring!

Alex
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