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

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.




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