Re: [RFC: DMA_PMD 00/22] DMA_PMD: PMD_SIZE-backed IO buffer pools

[Jakub Kicinski <kuba@kernel.org>]

On Fri, 23 Oct 2026 11:50:23 -0300 Jason Gunthorpe wrote:
> > Anyways, reading your next comments, are you suggesting that all
> > these functionalities should be implemented as pagepool extensions?
> > (2MB mappings and iommu backing, proper allocator of fragments out of larger
> > pages, device-less pagepools, multi-domain mappings, pagepool
> > as memory provider for skb heads, pagepool as memory provider for descriptor
> > rings ?)  
> 
> netdev shouldn't be touching iommu, it can get a 2M page and map it
> using the normal DMA API. AFAIK there is not such a big reason to need
> any of these layering violations. They just make it easier on page
> pool..

FWIW we're entirely happy on the netdev side to add this to page pool.
In fact the initial RFC I posted for "page pool memory providers"
was addressing this exact use case. I didn't push it forward due
to low time and suspicion that IOMMU folks would prefer a more generic
solution. Since then memory providers were pushed forward and merged
for dmabuf, and we have netlink APIs to configure things. So adding
large mappings should be SMOC.