Re: Build failure w/o mmu notifiers

[Avi Kivity <avi@redhat.com>]

Alexander Graf wrote:
>
> On 18.10.2008, at 12:51, Avi Kivity wrote:
>
>> Alexander Graf wrote:
>>>
>>> So if I don't select kvm in the kernel (either as module or compiled 
>>> in) I can't build an external module providing kvm's functionality? 
>>> That doesn't seem really useful to me...
>>>
>>
>> The external module hackball should detect that you don't have 
>> CONFIG_MMU_NOTIFIERS set and supply some compatibility glue.  What 
>> error are you seeing?
>
> Basically struct mmu_notifier is not found, but requested by the code:
>
> rm -f include/asm include-compat/asm
> ln -sf asm-x86 include/asm
> ln -sf asm-x86 include-compat/asm
> make -C /usr/src/linux-obj/i586/default M=`pwd` \
>         LINUXINCLUDE="-I`pwd`/include -Iinclude \
>         -Iinclude2 -I/lib/modules/2.6.27.1-2-default/source/include \
>         -Iarch/x86/include -I`pwd`/include-compat \
>         -include include/linux/autoconf.h \
>         -include `pwd`/x86/external-module-compat.h "
> make[1]: Entering directory `/usr/src/linux-2.6.27.1-2-obj/i386/default'
> make -C ../../../linux-2.6.27.1-2 
> O=/usr/src/linux-2.6.27.1-2-obj/i386/default/.
>   LD      
> /usr/src/packages/BUILD/kvm-77/suse-kernel/default/x86/built-in.o
>   CC [M]  /usr/src/packages/BUILD/kvm-77/suse-kernel/default/x86/svm.o
> In file included from 
> /usr/src/packages/BUILD/kvm-77/suse-kernel/default/x86/svm.c:16:
> /usr/src/packages/BUILD/kvm-77/suse-kernel/default/include/linux/kvm_host.h:128: 
> error: field 'mmu_notifier' has incomplete type
> make[5]: *** 
> [/usr/src/packages/BUILD/kvm-77/suse-kernel/default/x86/svm.o] Error 1
> make[4]: *** [/usr/src/packages/BUILD/kvm-77/suse-kernel/default/x86] 
> Error 2
> make[3]: *** 
> [_module_/usr/src/packages/BUILD/kvm-77/suse-kernel/default] Error 2
> make[2]: *** [sub-make] Error 2
> make[1]: *** [all] Error 2
> make[1]: Leaving directory `/usr/src/linux-2.6.27.1-2-obj/i386/default'
> make: *** [all] Error 2
> error: Bad exit status from /var/tmp/rpm-tmp.20019 (%build)
>
> When I remove the struct references it breaks later on due to 
> missing(?) inline functions.
>

Yes, there is an alternate definition in 
kernel/include-compat/linux/mmu_notifier.h, but it doesn't get included 
since the host's mmu_notifier.h has priority; and the host doesn't 
define the structure if !CONFIG_MMU_NOTIFIERS.

I recommend configuring the host with KVM and throwing the modules away 
if you want the external module.  You'll get better functionality so 
it's worth the minor hassle.

-- 
error compiling committee.c: too many arguments to function