On Tue, May 22, 2018 at 02:31:21PM -0700, Andrew Morton wrote: > On Tue, 22 May 2018 08:32:36 +0200 Christoph Hellwig <hch@xxxxxx> wrote: > > > On Mon, May 21, 2018 at 03:35:40PM -0700, Dan Williams wrote: > > > The routines hmm_devmem_add(), and hmm_devmem_add_resource() are small > > > wrappers around devm_memremap_pages(). The devm_memremap_pages() > > > interface is a subset of the hmm functionality which has more and deeper > > > ties into the kernel memory management implementation. It was an > > > oversight that these symbols were not marked EXPORT_SYMBOL_GPL from the > > > outset due to how they originally copied (and now reuse) > > > devm_memremap_pages(). > > > > If we end up keeping this code: absolutely. Then again I think without > > an actual user this should have never been merged, and should be removed > > until one shows up. > > > > It wasn't simple. Quite a lot of manufacturers were (are?) developing > quite complex driver code which utilizes hmm. Merging hmm to give a > stable target for that development and in the expectation that those > things would be coming along was a risk and I don't think we yet know > the outcome. > > Jerome, are you able to provide any updates on all of this? Sorry for taking so long to reply to this, I am just back from vacation. I posted a v1 for nouveau to use HMM back in April or early May. I want to post a v2 soon in June. For it to get upstream it needs to fullfill linux drm sub-system requirement which are an open source userspace for any functionality added to GPU driver. Work for this have been going on for a while too and userspace bits are slowly getting upstream inside Mesa. I need to sync up to see what is still missing in Mesa. So i won't be able to get nouveau HMM bits merge before the userspace bits are merge too. I was hopping for 4.18 but more likely 4.19. I know HMM have been a big chicken and egg thing and that timing for the egg did not match the timing for the chicken :) But it is getting there. Also I expect more hardware and associated upstream driver to make use of HMM but i can not comment further on that at this time because of NDA. Cheers, Jérôme
