[PATCH] drm/ttm: Temporarily disable the huge_fault() callback

[Dave Airlie]

On Fri, 10 Apr 2020 at 02:51, Thomas Hellström (VMware)
<thomas_os at shipmail.org> wrote:
>
> Dave, Christian,
>
> Could any of you pick this up (I'm currently on vacation) to have a
> chance of getting it in before -rc1?

I'll pull this in directly to fixes today.

Dave.

> Thanks,
> Thomas
>
>
> On 4/9/20 6:49 PM, Thomas Hellström (VMware) wrote:
> > From: "Thomas Hellstrom (VMware)" <thomas_os at shipmail.org>
> >
> > With amdgpu and CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS=y, there are
> > errors like:
> > BUG: non-zero pgtables_bytes on freeing mm
> > and:
> > BUG: Bad rss-counter state
> > with TTM transparent huge-pages.
> > Until we've figured out what other TTM drivers do differently compared to
> > vmwgfx, disable the huge_fault() callback, eliminating transhuge
> > page-table entries.
> >
> > Cc: Christian König <christian.koenig at amd.com>
> > Signed-off-by: Thomas Hellstrom (VMware) <thomas_os at shipmail.org>
> > Reported-by: Alex Xu (Hello71) <alex_y_xu at yahoo.ca>
> > Tested-by: Alex Xu (Hello71) <alex_y_xu at yahoo.ca>
> > Acked-by: Christian König <christian.koenig at amd.com>
> > ---
> >   drivers/gpu/drm/ttm/ttm_bo_vm.c | 63 ---------------------------------
> >   1 file changed, 63 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > index 6ee3b96f0d13..0ad30b112982 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > @@ -442,66 +442,6 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
> >   }
> >   EXPORT_SYMBOL(ttm_bo_vm_fault);
> >
> > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> > -/**
> > - * ttm_pgprot_is_wrprotecting - Is a page protection value write-protecting?
> > - * @prot: The page protection value
> > - *
> > - * Return: true if @prot is write-protecting. false otherwise.
> > - */
> > -static bool ttm_pgprot_is_wrprotecting(pgprot_t prot)
> > -{
> > -     /*
> > -      * This is meant to say "pgprot_wrprotect(prot) == prot" in a generic
> > -      * way. Unfortunately there is no generic pgprot_wrprotect.
> > -      */
> > -     return pte_val(pte_wrprotect(__pte(pgprot_val(prot)))) ==
> > -             pgprot_val(prot);
> > -}
> > -
> > -static vm_fault_t ttm_bo_vm_huge_fault(struct vm_fault *vmf,
> > -                                    enum page_entry_size pe_size)
> > -{
> > -     struct vm_area_struct *vma = vmf->vma;
> > -     pgprot_t prot;
> > -     struct ttm_buffer_object *bo = vma->vm_private_data;
> > -     vm_fault_t ret;
> > -     pgoff_t fault_page_size = 0;
> > -     bool write = vmf->flags & FAULT_FLAG_WRITE;
> > -
> > -     switch (pe_size) {
> > -     case PE_SIZE_PMD:
> > -             fault_page_size = HPAGE_PMD_SIZE >> PAGE_SHIFT;
> > -             break;
> > -#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
> > -     case PE_SIZE_PUD:
> > -             fault_page_size = HPAGE_PUD_SIZE >> PAGE_SHIFT;
> > -             break;
> > -#endif
> > -     default:
> > -             WARN_ON_ONCE(1);
> > -             return VM_FAULT_FALLBACK;
> > -     }
> > -
> > -     /* Fallback on write dirty-tracking or COW */
> > -     if (write && ttm_pgprot_is_wrprotecting(vma->vm_page_prot))
> > -             return VM_FAULT_FALLBACK;
> > -
> > -     ret = ttm_bo_vm_reserve(bo, vmf);
> > -     if (ret)
> > -             return ret;
> > -
> > -     prot = vm_get_page_prot(vma->vm_flags);
> > -     ret = ttm_bo_vm_fault_reserved(vmf, prot, 1, fault_page_size);
> > -     if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
> > -             return ret;
> > -
> > -     dma_resv_unlock(bo->base.resv);
> > -
> > -     return ret;
> > -}
> > -#endif
> > -
> >   void ttm_bo_vm_open(struct vm_area_struct *vma)
> >   {
> >       struct ttm_buffer_object *bo = vma->vm_private_data;
> > @@ -604,9 +544,6 @@ static const struct vm_operations_struct ttm_bo_vm_ops = {
> >       .open = ttm_bo_vm_open,
> >       .close = ttm_bo_vm_close,
> >       .access = ttm_bo_vm_access,
> > -#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> > -     .huge_fault = ttm_bo_vm_huge_fault,
> > -#endif
> >   };
> >
> >   static struct ttm_buffer_object *ttm_bo_vm_lookup(struct ttm_bo_device *bdev,
>
>