Am 06.08.19 um 22:03 schrieb Jason Gunthorpe: > On Tue, Aug 06, 2019 at 02:58:58PM -0400, Alex Deucher wrote: >> On Tue, Aug 6, 2019 at 1:51 PM Kuehling, Felix <Felix.Kuehling@xxxxxxx> wrote: >>> On 2019-08-06 13:44, Jason Gunthorpe wrote: >>>> On Tue, Aug 06, 2019 at 07:05:53PM +0300, Christoph Hellwig wrote: >>>>> The option is just used to select HMM mirror support and has a very >>>>> confusing help text. Just pull in the HMM mirror code by default >>>>> instead. >>>>> >>>>> Signed-off-by: Christoph Hellwig <hch@xxxxxx> >>>>> drivers/gpu/drm/Kconfig | 2 ++ >>>>> drivers/gpu/drm/amd/amdgpu/Kconfig | 10 ---------- >>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 6 ------ >>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h | 12 ------------ >>>>> 4 files changed, 2 insertions(+), 28 deletions(-) >>>> Felix, was this an effort to avoid the arch restriction on hmm or >>>> something? Also can't see why this was like this. >>> This option predates KFD's support of userptrs, which in turn predates >>> HMM. Radeon has the same kind of option, though it doesn't affect HMM in >>> that case. >>> >>> Alex, Christian, can you think of a good reason to maintain userptr >>> support as an option in amdgpu? I suspect it was originally meant as a >>> way to allow kernels with amdgpu without MMU notifiers. Now it would >>> allow a kernel with amdgpu without HMM or MMU notifiers. I don't know if >>> this is a useful thing to have. >> Right. There were people that didn't have MMU notifiers that wanted >> support for the GPU. > ?? Is that even a real thing? mmu_notifier does not have much kconfig > dependency. Yes, that used to be a very real thing. Initially a lot of users didn't wanted mmu notifiers to be enabled because of the performance overhead they costs. Then we had the problem that HMM mirror wasn't available on a lot of architectures. Not sure if we still need it separately, but I think that it shouldn't be removed without asking around if somebody still needs that. Christian. > > Jason
