Re: [Xen-devel] Re: Xen/ia64 presentation

[Hollis Blanchard <hollisb@xxxxxxxxxx>]

Keir Fraser wrote:
>> We've already seen that the only common code
>> using that type is to pass to (architecture-specific) show_registers().
> 
> Yes. Common code never dereferences cpu_user_regs, but it needs to
> receive it and pass it on.

Shrug, I don't mind things how they are, especially since Dan says it
works for him. It just seems silly to pass it everywhere for a single user.

>> x86 can get at its state by masking off ESP. PPC can get at it via
>> 'current'. Why then pass a pointer through all interrupt handlers when
>> none of them care?
> 
> No, that gets you an exec_domain (or 'vcpu', as we plan to rename it).
> Or it can get you the guest's cpu_user_regs. But if you interrupted a
> Xen activation then there is no way of getting at that outer
> activation's register state.

Ah, ok. I will have to think more about these activations.

> Even Linux has a pt_regs parameter passed to every interrupt handler, so
> it must surely be a good thing to do. ;-)

Yes yes... :)

-- 
Hollis Blanchard
IBM Linux Technology Center

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