Avi Kivity wrote:
> Zhang, Xiantao wrote:
>>>> For driver/kvm/kvm.h, I have a proposal before in mailing list.
>>>> In my proposal, we can split x86-specific code of kvm.h into
>>>> current x86.h, and make code in kvm.h as common. Then, we rename
>>>> kvm.h to kvm_comm.h, and also rename x86.h to kvm-x86.h, and
>>>> meantime kvm-x86.h would include kvm_comm.h. At compile time, we
>>>> can make symbol link for changing kvm-x86.h to kvm.h. So, it
>>>> should be more portable, because different archs can define its
>>>> kvm-$arch.h to hold its arch-specific code.
>>>>
>>>>
>>> I prefer not to have dynamic symlinks, it's too tricky.
>>>
>>> What's wrong with just the first part, x86.h which includes kvm.h?
>>> x86.c will include x86.h, and arch neutral files will include kvm.h.
>>>
>>
>> I think it may have issues. For example, where do we put struct
>> kvm_vcpu, and struct kvm? If we place them in x86.h, then kvm_main.c
>> and other neutral files can't reach it. If we put them in kvm.h,
>> how to handle arch-specific fields in them ?
>>
>
> Someone (I forget who) suggested using the same trick we use for vmx
> and svm. We nest as follows:
>
> struct vcpu_vmx {
> struct vcpu_x86 {
> struct kvm_vcpu {
> // common fields;
> } vcpu;
> // x86 specific fields;
> } x86;
> // vmx specific fields;
> };
>
> Allocation is done by arch specific code which allocates the outermost
> structure. Common code sees only kvm_vcpu and its fields. When it
> calls x86 arch hooks, they use the vcpu_x86() macro (which is a call
> to container_of()) to gain access to x86 specific fields. When x86
> code calls vmx specific code (using kvm_x86_ops), that uses
> vcpu_vmx() to gain access to the vmx specific fields. Any similarity
> to a language derived from C, living or dead, is purely coincidental
> and unintended.
Indeed a tricky way! From code logic, it should works well, but don't
know it is an elegant way to define such structure :-)
Xiantao
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