On Fri, Sep 13, 2019 at 03:05:34PM +0200, Thomas Zimmermann wrote:
> > +void ttm_bo_mmap_vma_setup(struct ttm_buffer_object *bo, struct vm_area_struct *vma)
> > +{
> > + vma->vm_ops = &ttm_bo_vm_ops;
> > +
> > + /*
> > + * Note: We're transferring the bo reference to
> > + * vma->vm_private_data here.
> > + */
> > +
> > + vma->vm_private_data = bo;
> > +
> > + /*
> > + * We'd like to use VM_PFNMAP on shared mappings, where
> > + * (vma->vm_flags & VM_SHARED) != 0, for performance reasons,
> > + * but for some reason VM_PFNMAP + x86 PAT + write-combine is very
> > + * bad for performance. Until that has been sorted out, use
> > + * VM_MIXEDMAP on all mappings. See freedesktop.org bug #75719
> > + */
> > + vma->vm_flags |= VM_MIXEDMAP;
> > + vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
> > +}
> > +EXPORT_SYMBOL(ttm_bo_mmap_vma_setup);
>
> To me, this function looks like an internal helper that should rather
> remain internal.
Well, I'm moving that to a helper exactly to avoid drm gem ttm helpers
messing with ttm internals. To not them initialize vm_flags for
example, and to avoid exporting ttm_bo_vm_ops. Also to make sure ttm bo
vma's are initialized the same way no matter which code path was taken
to mmap the object.
> As mentioned in my reply to patch 5, maybe re-using
> ttm_fbdev_mmap() could help.
No, the check in that function prevents that from working.
cheers,
Gerd
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