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Date:   Tue, 6 Jul 2021 18:06:58 +0100
From:   Will Deacon <will@kernel.org>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Christoph Hellwig <hch@lst.de>, heikki.krogerus@linux.intel.com,
        thomas.hellstrom@linux.intel.com, peterz@infradead.org,
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Subject: Re: [PATCH v15 06/12] swiotlb: Use is_swiotlb_force_bounce for
 swiotlb data bouncing
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On Tue, Jul 06, 2021 at 04:39:11PM +0100, Robin Murphy wrote:
> On 2021-07-06 15:05, 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.
> 
> Ah yes, that had slipped my mind, and it's a fair point indeed. Since we're
> not concerned with a minimal fix for backports anyway I'm more than happy to
> focus on Will's approach. Another thing is that that looks to take us a
> quiet step closer to the possibility of dynamically resizing a SWIOTLB pool,
> which is something that some of the hypervisor protection schemes looking to
> build on top of this series may want to explore at some point.

Ok, I'll split that nasty diff I posted up into a reviewable series and we
can take it from there.

Will