From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Gunthorpe <jgg@ziepe.ca>
Subject: Re: [PATCH 3/4] mm: simplify device private page handling in
 hmm_range_fault
Date: Mon, 16 Mar 2020 16:59:23 -0300
Message-ID: <20200316195923.GA26988@ziepe.ca>
References: <20200316193216.920734-1-hch@lst.de>
 <20200316193216.920734-4-hch@lst.de>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Return-path: <kvm-ppc-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <20200316193216.920734-4-hch@lst.de>
Sender: kvm-ppc-owner@vger.kernel.org
To: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>, Bharata B Rao <bharata@linux.ibm.com>, Christian =?utf-8?B?S8O2bmln?= <christian.koenig@amd.com>, Ben Skeggs <bskeggs@redhat.com>, Jerome Glisse <jglisse@redhat.com>, kvm-ppc@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-mm@kvack.org
List-Id: nouveau.vger.kernel.org

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