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[216.228.121.143]) by mx.google.com with ESMTPS id w8si433824ybo.234.2019.06.13.18.23.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Jun 2019 18:23:09 -0700 (PDT) Received-SPF: pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.143 as permitted sender) client-ip=216.228.121.143; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=CCd8e2Op; spf=pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.143 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate14.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 13 Jun 2019 18:23:08 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 13 Jun 2019 18:23:08 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 13 Jun 2019 18:23:08 -0700 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 14 Jun 2019 01:23:04 +0000 Subject: Re: [PATCH 18/22] mm: mark DEVICE_PUBLIC as broken 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 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> X-Nvconfidentiality: public From: John Hubbard Message-ID: Date: Thu, 13 Jun 2019 18:23:04 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190614004314.GD783@iweiny-DESK2.sc.intel.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL108.nvidia.com (172.18.146.13) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1560475388; bh=NWiGQvc0UaQg06vGlx/KBoyQY7FTb90HKZp/7cWu1+4=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=CCd8e2OpQNYk9MLkQj2SISKb1f8rHEt8owfBUnfdQ/EbQaEHFbssnQujsTCvu1hg/ mR8Y3/sQ0FeoXBKw8x7EwSNeP0JirtlvLprjUK1BAmudORUfLC87dyxEeAk19INas5 NI29MBs4mO8FUO+2r1avdCcLUMWD+OBag9RCJIoLc2O2dHRfWViTRDAYcfn3m6Wrf6 udfy6sC0OFEAlHI5edqKIVUfELxR84G7Dkf+roQu6aKqp3E13WZ1IqDdG/Lffgeh/e nogIq4wl7uO95KxuzvD0ijZERk5Gr6SxTkWBIiWMnMYA0zmWut5Pf3opqWtrNeceNW Ua0w/eL4F+pAQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org 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