Re: [RFC PATCH 0/3] generic hypercall support

Avi Kivity
2009-05-07T19:02:31Z

Gregory Haskins wrote:
> Avi Kivity wrote:
>
>> Gregory Haskins wrote:
>>
>>> I guess technically mmio can just be a simple access of the page which
>>> would be problematic to trap locally without a PF. However it seems
>>> that most mmio always passes through a ioread()/iowrite() call so this
>>> is perhaps the hook point. If we set the stake in the ground that mmios
>>> that go through some other mechanism like PFs can just hit the "slow
>>> path" are an acceptable casualty, I think we can make that work.
>>>
>>>
>> That's my thinking exactly.
>>
>
> Cool, I will code this up and submit it. While Im at it, Ill run it
> through the "nullio" ringer, too. ;) It would be cool to see the
> pv-mmio hit that 2.07us number. I can't think of any reason why this
> will not be the case.
>

Don't - it's broken. It will also catch device assignment mmio and
hypercall them.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.