Re: [PATCH 0 of 3] create kvm_x86

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Hollis Blanchard wrote:
>>
>> These cannot use the same method, since we need to support both vmx and
>> svm in the same binary.  The arch specific members aren't the same size,
>> nor do the symbols they use have the same visibility.
>>     
>
> I have never understood this. Why on earth do you need to support VMX
> and SVM in the same binary? For example, when would you overwrite
> kvm_x86_ops after initialization? If you wouldn't, then why are you
> using function pointers instead of the linker?
>   

Consider a non-modular build; common code needs to call either 
svm_vcpu_load() or vmx_vcpu_load() depending on the current hardware.

I imagine it could be done using linker tricks (duplicating the common 
code to be linked twice, once per subarch, and leaving a stub to detect 
which duplicate needs to be used), but I never found either the time or 
necessity to do them.

> PowerPC will also need to support multiple processor types, and so I
> expect to have one kvm_arch structure for each. That also means struct
> kvm_arch must be the *last* member in struct kvm, which is not how it is
> shown above.
>   

Do you plan to support multiple processor types in a single binary as 
well? Or require modules and compile them multiple times? (that was how 
AMD support was initially added; it was changed before merging).

-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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