Re: [PATCH] powerpc: convert 'iommu_alloc failed' messages to dynamic debug

Hi Ben,

On 06/13/2016 06:26 PM, Benjamin Herrenschmidt wrote:

I've been thinking about this a bit... it might be worthwhile adding
a dma_* call to query the approximate size of the IOMMU window, as
a way for the device to adjust its requirements dynamically.

Ok, cool; something like it was one of the options being discussed here.

What do you mean by 'approximate'? Maybe the size of 'free regions' in 
the pools? -- not sure because iiuic the window size is static / 2 gig,
so didn't get why (or of what) to provide an approximation (for).

Another option would be to use a dma_attr for silencing mapping errors
which NVME could use provided it does handle them gracefully ...

Ah, that's new. Interesting. Thanks for suggestion!


-- 
Mauricio Faria de Oliveira
IBM Linux Technology Center