Christoph Hellwig wrote: > On Wed, Sep 07, 2022 at 09:33:11AM -0300, Jason Gunthorpe wrote: > > Yes, you said that, and I said that when the AMD driver first merged > > it - but it went in anyhow and now people are using it in a bunch of > > places. > > drm folks made up their own weird rules, if they internally stick > to it they have to listen to it given that they ignore review comments, > but it violates the scatterlist API and has not business anywhere > else in the kernel. And yes, there probably is a reason or two why > the drm code is unusually error prone. > > > > Why would small BARs be problematic for the pages? The pages are more > > > a problem for gigantic BARs do the memory overhead. > > > > How do I get a struct page * for a 4k BAR in vfio? > > I guess we have different definitions of small then :) > > But unless my understanding of the code is out out of data, > memremap_pages just requires the (virtual) start address to be 2MB > aligned, not the size. Adding Dan for comments. The minimum granularity for sparse_add_section() that memremap_pages uses internally is 2MB, so start and end need to be 2MB aligned. Details here: ba72b4c8cf60 mm/sparsemem: support sub-section hotplug
