From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Gunthorpe Subject: Re: [PATCH 04/15] mm: remove the pgmap field from struct hmm_vma_walk Date: Thu, 15 Aug 2019 20:41:33 +0000 Message-ID: <20190815204128.GI22970@mellanox.com> References: <20190808065933.GA29382@lst.de> <20190814073854.GA27249@lst.de> <20190814132746.GE13756@mellanox.com> <20190815180325.GA4920@redhat.com> <20190815194339.GC9253@redhat.com> <20190815203306.GB25517@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20190815203306.GB25517@redhat.com> Content-Language: en-US Content-ID: <83C67FC496A7AF4DAD50FF0383D8AADD@eurprd05.prod.outlook.com> Sender: linux-kernel-owner@vger.kernel.org To: Jerome Glisse Cc: Dan Williams , Christoph Hellwig , Ben Skeggs , Felix Kuehling , Ralph Campbell , "linux-mm@kvack.org" , "nouveau@lists.freedesktop.org" , "dri-devel@lists.freedesktop.org" , "amd-gfx@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" List-Id: dri-devel@lists.freedesktop.org On Thu, Aug 15, 2019 at 04:33:06PM -0400, Jerome Glisse wrote: > So nor HMM nor driver should dereference the struct page (i do not > think any iommu driver would either), Er, they do technically deref the struct page: nouveau_dmem_convert_pfn(struct nouveau_drm *drm, struct hmm_range *range) struct page *page; page =3D hmm_pfn_to_page(range, range->pfns[i]); if (!nouveau_dmem_page(drm, page)) { nouveau_dmem_page(struct nouveau_drm *drm, struct page *page) { return is_device_private_page(page) && drm->dmem =3D=3D page_to_dmem(page) Which does touch 'page->pgmap' Is this OK without having a get_dev_pagemap() ? Noting that the collision-retry scheme doesn't protect anything here as we can have a concurrent invalidation while doing the above deref. Jason