Re: [PATCH] KVM: allow host header to be included even for !CONFIG_KVM

[Kevin Hilman]

Gleb Natapov <gleb@xxxxxxxxxx> writes:

> On Thu, Mar 21, 2013 at 02:33:13PM -0500, Scott Wood wrote:
>> On 03/21/2013 02:16:00 PM, Gleb Natapov wrote:
>> >On Thu, Mar 21, 2013 at 01:42:34PM -0500, Scott Wood wrote:
>> >> On 03/21/2013 09:27:14 AM, Kevin Hilman wrote:
>> >> >Gleb Natapov <gleb@xxxxxxxxxx> writes:
>> >> >
>> >> >> On Wed, Mar 20, 2013 at 06:58:41PM -0500, Scott Wood wrote:
>> >> >>> Why can't the entirety kvm_host.h be included regardless of
>> >> >>> CONFIG_KVM, just like most other feature-specific headers?  Why
>> >> >>> can't the if/else just go around the functions that you want to
>> >> >stub
>> >> >>> out for non-KVM builds?
>> >> >>>
>> >> >> Kevin,
>> >> >>
>> >> >>  What compilation failure this patch fixes? I presume
>> >something ARM
>> >> >> related.
>> >> >
>> >> >Not specficially ARM related, but more context tracking related
>> >since
>> >> >kernel/context_tracking.c pulls in kvm_host.h, which attempts to
>> >> >pull in
>> >> ><asm/kvm*.h> which may not exist on some platforms.
>> >> >
>> >> >At least for ARM, KVM support was added in v3.9 so this patch can
>> >> >probably be dropped since the non-KVM builds on ARM now work.
>> >But any
>> >> >platform without the <asm/kvm*.h> will still be broken when
>> >trying to
>> >> >build the context tracker.
>> >>
>> >> Maybe other platforms should get empty asm/kvm*.h files.  Is there
>> >> anything from those files that the linux/kvm*.h headers need to
>> >> build?
>> >>
>> >arch things. kvm_vcpu_arch, kvm_arch_memory_slot, kvm_arch etc.
>> 
>> Could define them as empty structs.
>> 
> Isn't is simpler for kernel/context_tracking.c to define empty
> __guest_enter()/__guest_exit() if !CONFIG_KVM.

I proposed something like that in an earlier version but Frederic asked
me to propose a fix to the KVM headers instead.

Just in case fixing the context tracking subsystem is preferred, 
the patch below fixes the problem also.

Kevin