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 Felix.Kuehling@amd.com 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@lst.de 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