On Fri, Sep 13, 2019 at 12:09 AM Thomas Hellström (VMware)
<thomas_os@xxxxxxxxxxxx> wrote:
>
> From: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
>
> Commit 4daa4fba3a38 ("gpu: drm: ttm: Adding new return type vm_fault_t")
> broke TTM prefaulting. Since vmf_insert_mixed() typically always returns
> VM_FAULT_NOPAGE, prefaulting stops after the second PTE.
>
> Restore (almost) the original behaviour. Unfortunately we can no longer
> with the new vm_fault_t return type determine whether a prefaulting
> PTE insertion hit an already populated PTE, and terminate the insertion
> loop. Instead we continue with the pre-determined number of prefaults.
>
> Fixes: 4daa4fba3a38 ("gpu: drm: ttm: Adding new return type vm_fault_t")
> Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Cc: Christian König <christian.koenig@xxxxxxx>
> Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
This commit merged into 4.19. Need to Cc stable.
Cc: stable@xxxxxxxxxxxxxxx # v4.19+
> ---
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 16 +++++++---------
> 1 file changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 5a580adeb9d1..aa18e8a53727 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -290,15 +290,13 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
> else
> ret = vmf_insert_pfn(&cvma, address, pfn);
>
> - /*
> - * Somebody beat us to this PTE or prefaulting to
> - * an already populated PTE, or prefaulting error.
> - */
> -
> - if (unlikely((ret == VM_FAULT_NOPAGE && i > 0)))
> - break;
> - else if (unlikely(ret & VM_FAULT_ERROR))
> - goto out_io_unlock;
> + /* Never error on prefaulted PTEs */
> + if (unlikely((ret & VM_FAULT_ERROR))) {
> + if (i == 0)
> + goto out_io_unlock;
> + else
> + break;
> + }
>
> address += PAGE_SIZE;
> if (unlikely(++page_offset >= page_last))
> --
> 2.20.1
>
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