Re: [PATCH] Clean up KVM/QEMU interaction

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Avi Kivity wrote:
> Anthony Liguori wrote:
>   
>> This patch attempts to clean up the interactions between KVM and QEMU.  Sorry
>> for such a big patch, but I don't think there's a better way to approach this
>> such that it's still bisect friendly.  I think this is most of what's needed to
>> get basic KVM support into QEMU though.
>>
>> Right now, there's a mix of #ifdef USE_KVM, if (kvm_allowed), and various
>> extern declarations.  It's all pretty fugly and there's a lot of mistakes due
>> to it.
>>
>> The following patch eliminates almost all uses of #ifdef USE_KVM by introducing
>> a kvm_enabled() macro.  If USE_KVM is set, this macro evaluates to kvm_allowed.
>> If USE_KVM isn't set, the macro evaluates to 0.
>>
>> Since GCC eliminates if (0) blocks, this is just as good as using #ifdef.  By
>> making sure that we never call into libkvm directly from QEMU, we can also just
>> not link qemu-kvm when USE_KVM isn't set instead of having the entire file
>> wrapped in a USE_KVM.
>>
>>   
>>     
>
> It might not when optimizations are disabled.  Please test.
>   

I did.  It works even without -O.

> Also, long term (when we're fully merged into qemu), we need to be able 
> to build without libkvm or linux/kvm.h installed.

With this patch (and the follow-ups), we can build without libkvm.  
There are only two places we call libkvm directly: in qemu-kvm-*.c or in 
some blocks guarded with KVM_CAP_*

I'll clean up the later with a follow up patch.

>   That means we can't 
> use any of the kvm.h defines and data structures.  So for example, 
> kvm_qemu_check_extension(KVM_CAP_USER_MEMORY)) needs to be changed to 
> kvm_qemu_supports_userspace_memory().
>   

Every place that makes that sort of call is guarded at the moment so it 
works.

Regards,

Anthony Liguori


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