From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [RFC PATCH 3/5] mm/vma: add support for peer to peer to device vma Date: Wed, 30 Jan 2019 19:19:52 +0000 Message-ID: <20190130191946.GD17080@mellanox.com> References: <20190129174728.6430-1-jglisse@redhat.com> <20190129174728.6430-4-jglisse@redhat.com> <20190129191120.GE3176@redhat.com> <20190129193250.GK10108@mellanox.com> <99c228c6-ef96-7594-cb43-78931966c75d@deltatee.com> <20190129205827.GM10108@mellanox.com> <20190130080208.GC29665@lst.de> <20190130174424.GA17080@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Language: en-US Content-ID: <2608ADBADE66244CAF93015265B4523A@eurprd05.prod.outlook.com> Sender: linux-kernel-owner@vger.kernel.org To: Logan Gunthorpe Cc: Christoph Hellwig , Jerome Glisse , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Greg Kroah-Hartman , "Rafael J . Wysocki" , Bjorn Helgaas , Christian Koenig , Felix Kuehling , "linux-pci@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Marek Szyprowski , Robin Murphy , Joerg Roedel , "iommu@lists.linux-foundation.org" List-Id: dri-devel@lists.freedesktop.org On Wed, Jan 30, 2019 at 11:13:11AM -0700, Logan Gunthorpe wrote: >=20 >=20 > On 2019-01-30 10:44 a.m., Jason Gunthorpe wrote: > > I don't see why a special case with a VMA is really that different. >=20 > Well one *really* big difference is the VMA changes necessarily expose > specialized new functionality to userspace which has to be supported > forever and may be difficult to change.=20 The only user change here is that more things will succeed when creating RDMA MRs (and vice versa to GPU). I don't think this restricts the kernel implementation at all, unless we intend to remove P2P entirely.. Jason