From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Date: Wed, 31 Mar 2021 13:46:04 +0000 Subject: Re: [PATCH v7 5/8] mm: Device exclusive memory access Message-Id: <20210331134604.GK1463678@nvidia.com> List-Id: References: <20210326000805.2518-1-apopple@nvidia.com> <2521635.masqiumSp9@nvdebian> <20210331131854.GI1463678@nvidia.com> <2124945.3NMGunUBXV@nvdebian> In-Reply-To: <2124945.3NMGunUBXV@nvdebian> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Alistair Popple Cc: linux-mm@kvack.org, nouveau@lists.freedesktop.org, bskeggs@redhat.com, akpm@linux-foundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kvm-ppc@vger.kernel.org, dri-devel@lists.freedesktop.org, jhubbard@nvidia.com, rcampbell@nvidia.com, jglisse@redhat.com, hch@infradead.org, daniel@ffwll.ch, willy@infradead.org, Christoph Hellwig On Thu, Apr 01, 2021 at 12:27:52AM +1100, Alistair Popple wrote: > On Thursday, 1 April 2021 12:18:54 AM AEDT Jason Gunthorpe wrote: > > On Wed, Mar 31, 2021 at 11:59:28PM +1100, Alistair Popple wrote: > > > > > I guess that makes sense as the split could go either way at the > > > moment but I should add a check to make sure this isn't used with > > > pinned pages anyway. > > > > Is it possible to have a pinned page under one of these things? If I > > pin it before you migrate it then it remains pinned but hidden under > > the swap entry? > > At the moment yes. But I had planned (and this reminded me) to add a check to > prevent marking pinned pages for exclusive access. How do you even do that without races with GUP fast? Jason