Re: [Qemu-devel] [PATCH 12/25] target-sparc: Add MMU_REAL_IDX

[Richard Henderson]

On 01/15/2016 12:32 PM, Artyom Tarasenko wrote:
>> If we ever properly implement a sun4v platform, we will implement the bulk of
>> the hypervisor within qemu itself, for speed.  At which point REAL will in 
>> fact
>> undergo that final layer of translation exactly as expected.
>>
>> I think the naming is exactly correct, for the current sun4u implementation.
> 
> But sun4u has neither real mode nor any ASI having "real" as a part of
> its name, no?

Correct-ish.  The ASI is called ASI_PHYS_USE_EC.  But it has the same number as
ASI_REAL.  When there's a conflict I'm preferring the newer names.  I think
that it will cause less confusion in the end.


> I thought it is much easier to implement the RA translation than the 
> hypervisor,
> but maybe implementing the hypervisor is not as complex as I thought.
> 
> Indeed, your variant would be more performant.
> In any case it looks like an interesting challenge.

The Alpha PALcode layer (equivalent to the sun4v hypervisor) is 99% implemented
in qemu, and performs significantly better because of it.
There are a few stubs in the qemu bios calling into some special helpers; I'd
expect OpenBIOS for qemu to be the same.



r~