From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH 15/15] amdgpu: remove CONFIG_DRM_AMDGPU_USERPTR Date: Wed, 7 Aug 2019 08:46:33 -0300 Message-ID: <20190807114633.GA1557@ziepe.ca> References: <20190806160554.14046-1-hch@lst.de> <20190806160554.14046-16-hch@lst.de> <20190806174437.GK11627@ziepe.ca> <587b1c3c-83c4-7de9-242f-6516528049f4@amd.com> <20190806200356.GU11627@ziepe.ca> <4a040a3f-8981-3e94-2436-8295a0caa534@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4a040a3f-8981-3e94-2436-8295a0caa534@amd.com> Sender: linux-kernel-owner@vger.kernel.org To: "Koenig, Christian" Cc: Alex Deucher , "Kuehling, Felix" , Christoph Hellwig , "Deucher, Alexander" , Ralph Campbell , "amd-gfx@lists.freedesktop.org" , "nouveau@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linux-mm@kvack.org" , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Ben Skeggs List-Id: dri-devel@lists.freedesktop.org On Wed, Aug 07, 2019 at 06:57:24AM +0000, Koenig, Christian wrote: > 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 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 > >>>>> 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. Seems strange to hear these days, every distro ships with it on, it is needed for kvm. > Then we had the problem that HMM mirror wasn't available on a lot of > architectures. Some patches for hmm are ready now that will fix this Jason