From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hqemgate14.nvidia.com (hqemgate14.nvidia.com [216.228.121.143]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 89DB121959CB2 for ; Thu, 13 Jun 2019 18:23:08 -0700 (PDT) Subject: Re: [PATCH 18/22] mm: mark DEVICE_PUBLIC as broken References: <20190613094326.24093-1-hch@lst.de> <20190613094326.24093-19-hch@lst.de> <20190613194430.GY22062@mellanox.com> <20190613195819.GA22062@mellanox.com> <20190614004314.GD783@iweiny-DESK2.sc.intel.com> From: John Hubbard Message-ID: Date: Thu, 13 Jun 2019 18:23:04 -0700 MIME-Version: 1.0 In-Reply-To: <20190614004314.GD783@iweiny-DESK2.sc.intel.com> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Ira Weiny , Jason Gunthorpe Cc: Ralph Campbell , "linux-nvdimm@lists.01.org" , "nouveau@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linux-mm@kvack.org" , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Ben Skeggs , "linux-pci@vger.kernel.org" , Christoph Hellwig List-ID: On 6/13/19 5:43 PM, Ira Weiny wrote: > On Thu, Jun 13, 2019 at 07:58:29PM +0000, Jason Gunthorpe wrote: >> On Thu, Jun 13, 2019 at 12:53:02PM -0700, Ralph Campbell wrote: >>> ... >> Hum, so the only thing this config does is short circuit here: >> >> static inline bool is_device_public_page(const struct page *page) >> { >> return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) && >> IS_ENABLED(CONFIG_DEVICE_PUBLIC) && >> is_zone_device_page(page) && >> page->pgmap->type == MEMORY_DEVICE_PUBLIC; >> } >> >> Which is called all over the place.. > > yes but the earlier patch: > > [PATCH 03/22] mm: remove hmm_devmem_add_resource > > Removes the only place type is set to MEMORY_DEVICE_PUBLIC. > > So I think it is ok. Frankly I was wondering if we should remove the public > type altogether but conceptually it seems ok. But I don't see any users of it > so... should we get rid of it in the code rather than turning the config off? > > Ira That seems reasonable. I recall that the hope was for those IBM Power 9 systems to use _PUBLIC, as they have hardware-based coherent device (GPU) memory, and so the memory really is visible to the CPU. And the IBM team was thinking of taking advantage of it. But I haven't seen anything on that front for a while. So maybe it will get re-added as part of a future patchset to use that kind of memory, but yes, we should not hesitate to clean house at this point, and delete unused code. thanks, -- John Hubbard NVIDIA > >> >> So, yes, we really don't want any distro or something to turn this on >> until it has a use. >> >> Reviewed-by: Jason Gunthorpe >> >> Jason >> _______________________________________________ >> Linux-nvdimm mailing list >> Linux-nvdimm@lists.01.org >> https://lists.01.org/mailman/listinfo/linux-nvdimm _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm