From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f197.google.com (mail-qt0-f197.google.com [209.85.216.197]) by kanga.kvack.org (Postfix) with ESMTP id DD9E86B02E1 for ; Tue, 25 Apr 2017 03:08:47 -0400 (EDT) Received: by mail-qt0-f197.google.com with SMTP id j29so46328423qtj.19 for ; Tue, 25 Apr 2017 00:08:47 -0700 (PDT) Received: from edison.jonmasters.org (edison.jonmasters.org. [173.255.233.168]) by mx.google.com with ESMTPS id e126si21051469qkb.62.2017.04.25.00.08.47 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 25 Apr 2017 00:08:47 -0700 (PDT) References: <20170422033037.3028-1-jglisse@redhat.com> <20170422033037.3028-4-jglisse@redhat.com> <20170422181151.GA2360@redhat.com> From: Jon Masters Message-ID: Date: Tue, 25 Apr 2017 03:08:43 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [HMM 03/15] mm/unaddressable-memory: new type of ZONE_DEVICE for unaddressable memory Sender: owner-linux-mm@kvack.org List-ID: To: John Hubbard , Dan Williams , Jerome Glisse Cc: Andrew Morton , "linux-kernel@vger.kernel.org" , Linux MM , Naoya Horiguchi , David Nellans , Ross Zwisler On 04/23/2017 08:39 PM, John Hubbard wrote: > Actually, MEMORY_DEVICE_PRIVATE / _PUBLIC seems like a good choice to > me, because the memory may not remain CPU-unaddressable in the future. > By that, I mean that I know of at least one company (ours) that is > working on products that will support hardware-based memory coherence > (and access counters to go along with that). If someone were to enable > HMM on such a system, then the device memory would be, in fact, directly > addressable by a CPU--thus exactly contradicting the "unaddressable" name. I'm expecting similar with CCIX-like coherently attached accelerators running within FPGAs and as discrete devices as well. Everyone and their dog is working on hardware based coherence as a programming convenience and so the notion of ZONE_DEVICE as it stood is going to rapidly evolve over the next 18 months, maybe less. Short term anyway. Jon. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org