Hi Nirmoy, On Tue, Mar 26, 2024 at 01:05:37PM +0100, Nirmoy Das wrote: > On 3/26/2024 12:12 PM, Andi Shyti wrote: > > > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c > > > > index a2195e28b625..57a2dda2c3cc 100644 > > > > --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c > > > > +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c > > > > @@ -276,7 +276,7 @@ static vm_fault_t vm_fault_cpu(struct vm_fault *vmf) > > > > /* PTEs are revoked in obj->ops->put_pages() */ > > > > err = remap_io_sg(area, > > > > area->vm_start, area->vm_end - area->vm_start, > > > > - obj->mm.pages->sgl, iomap); > > > > + obj->mm.pages->sgl, 0, iomap); > > > Why don't we need partial mmap for CPU but only for GTT ? > > As far as I understood we don't. I have a version with the CPU > > offset as well in trybot[*] > > > > But without support for segmented buffer objects, I don't know > > how much this has any effect. > > You confused me more :) Why segmented buffer object is needed for partial > CPU mmap but not for GTT ? atually segmented bo's were introduced to support single dma buffers instead of fragmented buffers. But this goes beyond the scope of this patch. > From high level, GTT and CPU both should support partial mmap unless I > missing something here. But yes, we could take the patch I linked which adds some offset to the cpu memory. I will add it in V2. > > > > > Sounds like this also need to be cover by a IGT tests. > > Yes, I it does need some igt work, working on it. > > > > > Don't we need "Fixes" tag for this? > > Why should we? I'm not fixing anything here, > > If userspace expects partial mmap to work then this is a bug/gap in i915 so > we need to > > backport this as far as possible. Need some information about the > requirement about why we need this patch suddenly? But a gap is not a bug. Theoretically we are adding a feature. On the other hand it would be a bug if the API promises to add the offset but in reality it doesn't. I will check if this is the case and it needs to be well described in the commit message. Thanks, Andi
