Re: [PATCH] arm64: Enable PCI write-combine resources under sysfs

Clint Sbisa
2020-09-14T22:32:38Z

On Tue, Sep 15, 2020 at 08:00:27AM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2020-09-15 at 07:42 +1000, Benjamin Herrenschmidt wrote:
> >
> > > which is back to my original question, how do you do DMA using
> > > /sys/xx/resources? Why not use VFIO like everything else?
> >
> > Note: All this doesnt' change the fact that sys/xx/resources_wc
> > exists
> > for other archs and I see no reasons so far not to have it on ARM...
>
> Also... it looks like VFIO also doesn't provide a way to do WC yet
> unfortunately :-(
>
> There was a discussion 2 or 3 years ago while I was at IBM about ways
> to add that functionality, but it doesn't seem to have resulted in
> anything.

And to complete answering the question, the ENA PMD in DPDK also supports vfio,
which-- as Ben pointed out-- doesn't support WC either.

Clint