[PATCH 3/4] mm: simplify device private page handling in hmm_range_fault

[Jason Gunthorpe]

On Mon, Mar 16, 2020 at 08:32:15PM +0100, Christoph Hellwig wrote:
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 180e398170b0..cfad65f6a67b 100644
> +++ b/mm/hmm.c
> @@ -118,15 +118,6 @@ static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
>  	/* We aren't ask to do anything ... */
>  	if (!(pfns & range->flags[HMM_PFN_VALID]))
>  		return;
> -	/* If this is device memory then only fault if explicitly requested */
> -	if ((cpu_flags & range->flags[HMM_PFN_DEVICE_PRIVATE])) {
> -		/* Do we fault on device memory ? */
> -		if (pfns & range->flags[HMM_PFN_DEVICE_PRIVATE]) {
> -			*write_fault = pfns & range->flags[HMM_PFN_WRITE];
> -			*fault = true;
> -		}
> -		return;
> -	}

Yes, this is an elegant solution to the input flags.

However, between patch 3 and 4 doesn't this break amd gpu as it will
return device_private pages now if not requested? Squash the two?

Jason