linux-kernel - Re: [GIT PULL -tip v3] fix 39 'make headers

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Message-ID: <497469AC.2030107@redhat.com>
Date:	Mon, 19 Jan 2009 13:53:16 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Sam Ravnborg <sam@...nborg.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL -tip v3] fix 39 'make headers_check' warnings

Sam Ravnborg wrote:
>> They are.  This bits advertise to userspace what features kvm supports, 
>> both compile- and run-time.
>>     
>
> This is wrong...
> The headers does not change with the kernel configuration and advertising the
> kvm features via a .h file like this is simply plain broken.
>   

Ok.  Don't know why I thought unifdef was supplied with the full 
configuration.

> You cannot assume that the header files are generated with the exact same config
> as used by the running kernel.
>   

This is just for arch specific defines.  I'll move these to asm/kvm.h.

> And userspace has in no way access to the CONFIG_ namespace which is purely kernel-internal.
>
> I cannot see how you have ever seen kcm advertise that for example KVM_CAP_USER_NMI
> equals to 22 because CONFIG_X86 is never (supposed to be) defined in userspace -
> except if you did so yourself by some means.
>   

We did, we ship a hacked-up kvm.h (generated by unifdef) with our userspace.

Thanks for the clarifications, helpful as always.

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

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