Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist

[Christoph Hellwig]

On Tue, Nov 06, 2018 at 02:39:26PM +0000, Robin Murphy wrote:
> ...and I have some significant objections to that simplification which I
> plan to respond with ;)
> 
> (namely that it defaults the whole higher-order page allocation business
> which will have varying degrees of performance impact on certain cases)

Well, please place your objection there.  The behavior does match what
every other iommu-based dma ops implementation ouside of arm/arm64 does,
so there is some precedent for it to say the least.  But if the only
current users objects I'll surely find a way to accomodate it, but a
good rationale including numbers would be useful to document it.