Re: [PATCH v15 06/12] swiotlb: Use is_swiotlb_force_bounce for swiotlb data bouncing

From: Konrad Rzeszutek Wilk
Date: Tue Jul 06 2021 - 10:48:37 EST

On Tue, Jul 06, 2021 at 04:05:13PM +0200, Christoph Hellwig wrote:
> On Tue, Jul 06, 2021 at 03:01:04PM +0100, Robin Murphy wrote:
> > FWIW I was pondering the question of whether to do something along those
> > lines or just scrap the default assignment entirely, so since I hadn't got
> > round to saying that I've gone ahead and hacked up the alternative
> > (similarly untested) for comparison :)
> >
> > TBH I'm still not sure which one I prefer...
> Claire did implement something like your suggestion originally, but
> I don't really like it as it doesn't scale for adding multiple global
> pools, e.g. for the 64-bit addressable one for the various encrypted
> secure guest schemes.

Couple of things:
- I am not pushing to Linus the Claire's patchset until we have a
resolution on this. I hope you all agree that is a sensible way
forward as much as I hate doing that.

- I like Robin's fix as it is simplest looking. Would love to see if it
does fix the problem.

- Christopher - we can always add multiple pools as the next milestone
and just focus on this feature getting tested extensively during this

- Would it be worth (for future or maybe in another tiny fix) to also add
a printk in swiotlb when we de-allocate the buffer so when someone looks
through the `dmesg` it becomes much easier to diagnose issues?