On Mon, Mar 07, 2022 at 11:12:44AM +0100, David Hildenbrand wrote: > On 06.03.22 06:32, Jarkko Sakkinen wrote: > > For device memory (aka VM_IO | VM_PFNMAP) MAP_POPULATE does nothing. Allow > > to use that for initializing the device memory by providing a new callback > > f_ops->populate() for the purpose. > > > > SGX patches are provided to show the callback in context. > > > > An obvious alternative is a ioctl but it is less elegant and requires > > two syscalls (mmap + ioctl) per memory range, instead of just one > > (mmap). > > What about extending MADV_POPULATE_READ | MADV_POPULATE_WRITE to support > VM_IO | VM_PFNMAP (as well?) ? What would be a proper point to bind that behaviour? For mmap/mprotect it'd be probably populate_vma_page_range() because that would span both mmap() and mprotect() (Dave's suggestion in this thread). For MAP_POPULATE I did not have hard proof to show that it would be used by other drivers but for madvice() you can find at least a few ioctl based implementations: $ git grep -e madv --and \( -e ioc \) drivers/ drivers/gpu/drm/i915/gem/i915_gem_ioctls.h:int i915_gem_madvise_ioctl(struct drm_device *dev, void *data, drivers/gpu/drm/i915/i915_driver.c: DRM_IOCTL_DEF_DRV(I915_GEM_MADVISE, i915_gem_madvise_ioctl, DRM_RENDER_ALLOW), drivers/gpu/drm/i915/i915_gem.c:i915_gem_madvise_ioctl(struct drm_device *dev, void *data, drivers/gpu/drm/msm/msm_drv.c:static int msm_ioctl_gem_madvise(struct drm_device *dev, void *data, drivers/gpu/drm/msm/msm_drv.c: DRM_IOCTL_DEF_DRV(MSM_GEM_MADVISE, msm_ioctl_gem_madvise, DRM_RENDER_ALLOW), drivers/gpu/drm/panfrost/panfrost_drv.c:static int panfrost_ioctl_madvise(struct drm_device *dev, void *data, drivers/gpu/drm/vc4/vc4_drv.c: DRM_IOCTL_DEF_DRV(VC4_GEM_MADVISE, vc4_gem_madvise_ioctl, DRM_RENDER_ALLOW), drivers/gpu/drm/vc4/vc4_drv.h:int vc4_gem_madvise_ioctl(struct drm_device *dev, void *data, drivers/gpu/drm/vc4/vc4_gem.c:int vc4_gem_madvise_ioctl(struct drm_device *dev, void *data, IMHO this also provides supportive claim for MAP_POPULATE, and yeah, I agree that to be consistent implementation, both madvice() and MAP_POPULATE should work. > -- > Thanks, > > David / dhildenb BR, Jarkko
