RE: [Xen-ia64-devel] Re: [Xen-devel] XenLinux/IA64 domU forward port

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

Great progress!

> 
> Eddie, I haven't forgotten your discussion.
> I think it is necessary to get linux-ia64 people involved for
> the discussion. The concrete patch is needed.

Yes, so are you planing to push pv_ops based solution or
binary patching based solution? My basic understanding to
redhat's concern is that they want to adopt similar approach
in IA64 side together with X86, which uses pv_ops.

> Once I split the patch up, I'll post them to linux-ia64 so that we
> can start the discussion with them.
> My vague idea is as follows.
> - For neutral paravirtualization api, some kind of ABI is necessary.
> - It would need some kind of static calling convention.
> - Currently the nearest standard is PAL static calling convention.
>   So far I agree with you.
> - PAL static calling convention uses banked registers(r16-r31) as
>   arguments. However it would be suboptimal or unsuitable for
>   paravirtualization ABI. Static and non-banked registers are
>   desirable.(at least for Xen) so that r9-r11, r14-r15 are desirable.

We can't destroy non bank0 register in interrupt/exception handler
before memory based storage is involved to save/restore them. 
That is why I'd like to limit those parameters to bank0 registers.
For current Xen, it is using kind of C ABI (i.e. R8/R9), we can argu
if it is best, but should be easy to commodate both.

thx, eddue



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