Re: [RFC PATCH V3 0/5] Hi:

Jason Wang
2019-01-08T10:12:38Z

On 2019/1/7 下午10:47, Michael S. Tsirkin wrote:
> On Mon, Jan 07, 2019 at 02:58:08PM +0800, Jason Wang wrote:
>> On 2019/1/5 上午5:41, Michael S. Tsirkin wrote:
>>> On Sat, Dec 29, 2018 at 08:46:51PM +0800, Jason Wang wrote:
>>>> This series tries to access virtqueue metadata through kernel virtual
>>>> address instead of copy_user() friends since they had too much
>>>> overheads like checks, spec barriers or even hardware feature
>>>> toggling.
>>> I think it's a reasonable approach.
>>> However I need to look at whether and which mmu notifiers are invoked before
>>> writeback. Do you know?
>>
>> I don't know but just looking at the MMU notifier ops definition, there's no
>> such callback if my understanding is correct.
>>
>> Thanks
> In that case how are you making sure used ring updates are written back?
> If they aren't guest will crash ...

I think this is the writeback issue you mentioned early. I don't do a
followup on the pointer but it looks to me some work is ongoing to fix
the issue.

I can investigate it more, but it's not something new, consider the case
of VFIO.

Thanks