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

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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 ;-).

Alex

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