Re: [PATCH net 2/2] page_pool: fix IOMMU crash when driver has already unbound

[Ilias Apalodimas <ilias.apalodimas@linaro.org>]

Hi Jason,

On Mon, 23 Sept 2024 at 20:52, Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Fri, Sep 20, 2024 at 02:14:02PM +0800, Yunsheng Lin wrote:
>
> > I am not sure what dose the API that allows netdev to "give" struct device
> > to page_pool look like or how to implement the API yet, but the obvious way
> > to stall the calling of device_del() is to wait for the inflight
> > page to
>
> It is not device_del() you need to stall, but the remove() function of
> the device driver.
>
> Once all drivers have been unbound the DMA API can be reconfigured and
> all existing DMA mappings must be concluded before this happens,
> otherwise there will be problems.
>
> So, stalling something like unregister_netdevice() would be a better
> target - though stalling forever on driver unbind would not be
> acceptable.

TBH, I have doubts that even stalling it for small amounts of time is
going to disrupt userspace and people are going to yell at us.
I am gonna repeat myself here, but I think keeping a list of the
inflight SKBs that we need to unmap when the interface goes down, is
the most complex, but less disruptive solution

Thanks
/Ilias
>
> Jason