Re: [PATCH 2/3] drm/amdgpu: block THP for HSA userptr notifiers

[Christian König]

On 6/25/26 12:59, Yitao Jiang wrote:
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> 
> HSA userptr buffer objects are used by KFD compute queues. On systems
> where the GPU cannot reliably tolerate a CPU THP remap of an active
> userptr range, allowing khugepaged or MADV_COLLAPSE to replace PTE
> mappings with a PMD mapping can leave later GPU work failing
> asynchronously.

Absolutely clear NAK to this.

That largely sounds like it just work around some issue and is not really a doable fix.

Regards,
Christian.

> 
> Register HSA userptr interval notifiers with
> MMU_INTERVAL_NOTIFIER_BLOCK_THP. GFX userptrs keep the existing
> notifier path and do not opt in.
> 
> Assisted-by: OpenAI-Codex:GPT-5.5
> Signed-off-by: Yitao Jiang <jytscientist@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
> index 99bc9ad67..c0b36164c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
> @@ -44,6 +44,7 @@
>   */
> 
>  #include <linux/firmware.h>
> +#include <linux/mm.h>
>  #include <linux/module.h>
>  #include <drm/drm.h>
> 
> @@ -130,16 +131,24 @@ static const struct mmu_interval_notifier_ops amdgpu_hmm_hsa_ops = {
>   */
>  int amdgpu_hmm_register(struct amdgpu_bo *bo, unsigned long addr)
>  {
> +       struct mm_struct *mm = current->mm;
> +       unsigned long size = amdgpu_bo_size(bo);
>         int r;
> 
> -       if (bo->kfd_bo)
> -               r = mmu_interval_notifier_insert(&bo->notifier, current->mm,
> -                                                   addr, amdgpu_bo_size(bo),
> -                                                   &amdgpu_hmm_hsa_ops);
> -       else
> -               r = mmu_interval_notifier_insert(&bo->notifier, current->mm, addr,
> -                                                       amdgpu_bo_size(bo),
> -                                                       &amdgpu_hmm_gfx_ops);
> +       if (unlikely(!mm))
> +               return -ESRCH;
> +
> +       if (bo->kfd_bo) {
> +               mmap_write_lock(mm);
> +               r = mmu_interval_notifier_insert_locked_flags(&bo->notifier, mm,
> +                                                             addr, size,
> +                                                             &amdgpu_hmm_hsa_ops,
> +                                                             MMU_INTERVAL_NOTIFIER_BLOCK_THP);
> +               mmap_write_unlock(mm);
> +       } else {
> +               r = mmu_interval_notifier_insert(&bo->notifier, mm, addr, size,
> +                                                &amdgpu_hmm_gfx_ops);
> +       }
>         if (r)
>                 /*
>                  * Make sure amdgpu_hmm_unregister() doesn't call
> --
> 2.53.0
>