From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B50BC433F5 for ; Mon, 13 Dec 2021 07:49:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232624AbhLMHt1 (ORCPT ); Mon, 13 Dec 2021 02:49:27 -0500 Received: from verein.lst.de ([213.95.11.211]:46497 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232561AbhLMHtZ (ORCPT ); Mon, 13 Dec 2021 02:49:25 -0500 Received: by verein.lst.de (Postfix, from userid 2407) id 0BC3D68AFE; Mon, 13 Dec 2021 08:49:20 +0100 (CET) Date: Mon, 13 Dec 2021 08:49:19 +0100 From: Christoph Hellwig To: Baoquan He Cc: Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, robin.murphy@arm.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, m.szyprowski@samsung.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org Subject: Re: [PATCH RESEND v2 0/5] Avoid requesting page from DMA zone when no managed pages Message-ID: <20211213074919.GC20758@lst.de> References: <20211207030750.30824-1-bhe@redhat.com> <20211209080540.GA3050@MiWiFi-R3L-srv> <20211213073925.GA29905@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211213073925.GA29905@MiWiFi-R3L-srv> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 13, 2021 at 03:39:25PM +0800, Baoquan He wrote: > > > As said at above, ia64 and riscv don't have ZONE_DMA at all, they just > > > cover low 4G with ZONE_DMA32 alone. > > > > If you do not have devices that are crap and cannot address the full > > memory then you dont need these special zones. > > I am not a DMA expert, with my understanding, on x86_64 and arm64, we > have PCIe devices which dma mask is 32bit Yes, way to many, and they keep getting newly introduce as well. Also weirdo masks like 40, 44 or 48 bits. > , means they can only address > ZONE_DMA32. Yes and no. Offset between cpu physical and device address make this complicated, even ignoring iommus. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mwg5N-0089o3-6h for kexec@lists.infradead.org; Mon, 13 Dec 2021 07:49:26 +0000 Date: Mon, 13 Dec 2021 08:49:19 +0100 From: Christoph Hellwig Subject: Re: [PATCH RESEND v2 0/5] Avoid requesting page from DMA zone when no managed pages Message-ID: <20211213074919.GC20758@lst.de> References: <20211207030750.30824-1-bhe@redhat.com> <20211209080540.GA3050@MiWiFi-R3L-srv> <20211213073925.GA29905@MiWiFi-R3L-srv> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211213073925.GA29905@MiWiFi-R3L-srv> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Baoquan He Cc: Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, hch@lst.de, robin.murphy@arm.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, m.szyprowski@samsung.com, John.p.donnelly@oracle.com, kexec@lists.infradead.org On Mon, Dec 13, 2021 at 03:39:25PM +0800, Baoquan He wrote: > > > As said at above, ia64 and riscv don't have ZONE_DMA at all, they just > > > cover low 4G with ZONE_DMA32 alone. > > > > If you do not have devices that are crap and cannot address the full > > memory then you dont need these special zones. > > I am not a DMA expert, with my understanding, on x86_64 and arm64, we > have PCIe devices which dma mask is 32bit Yes, way to many, and they keep getting newly introduce as well. Also weirdo masks like 40, 44 or 48 bits. > , means they can only address > ZONE_DMA32. Yes and no. Offset between cpu physical and device address make this complicated, even ignoring iommus. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec