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[213.95.11.211]) by mx.google.com with ESMTPS id z11si56430075wmi.85.2019.08.01.07.08.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Aug 2019 07:08:23 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) client-ip=213.95.11.211; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of hch@lst.de designates 213.95.11.211 as permitted sender) smtp.mailfrom=hch@lst.de Received: by verein.lst.de (Postfix, from userid 2407) id 7FDE168AFE; Thu, 1 Aug 2019 16:08:20 +0200 (CEST) Date: Thu, 1 Aug 2019 16:08:20 +0200 From: Christoph Hellwig To: Nicolas Saenz Julienne Cc: catalin.marinas@arm.com, hch@lst.de, wahrenst@gmx.net, marc.zyngier@arm.com, Robin Murphy , linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, iommu@lists.linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, phill@raspberryi.org, f.fainelli@gmail.com, will@kernel.org, robh+dt@kernel.org, eric@anholt.net, mbrugger@suse.com, akpm@linux-foundation.org, frowand.list@gmail.com, m.szyprowski@samsung.com, linux-rpi-kernel@lists.infradead.org Subject: Re: [PATCH 8/8] mm: comment arm64's usage of 'enum zone_type' Message-ID: <20190801140820.GC23435@lst.de> References: <20190731154752.16557-1-nsaenzjulienne@suse.de> <20190731154752.16557-9-nsaenzjulienne@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190731154752.16557-9-nsaenzjulienne@suse.de> User-Agent: Mutt/1.5.17 (2007-11-01) 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 Wed, Jul 31, 2019 at 05:47:51PM +0200, Nicolas Saenz Julienne wrote: > + * Architecture Limit > + * ---------------------------------- > + * parisc, ia64, sparc, arm64 <4G > + * s390, powerpc <2G > + * arm Various > + * alpha Unlimited or 0-16MB. > * > * i386, x86_64 and multiple other arches > - * <16M. > + * <16M. powerpc is also Various now, arm64 isn't really < 4G, ia64 only uses ZONE_DMA32 these days, and parisc doesn't seem to use neither ZONE_DMA nor ZONE_DMA32. Based on that I'm not sure the list really makes much sense. > */ > ZONE_DMA, > #endif > #ifdef CONFIG_ZONE_DMA32 > /* > - * x86_64 needs two ZONE_DMAs because it supports devices that are > - * only able to do DMA to the lower 16M but also 32 bit devices that > - * can only do DMA areas below 4G. > + * x86_64 and arm64 need two ZONE_DMAs because they support devices > + * that are only able to DMA a fraction of the 32 bit addressable > + * memory area, but also devices that are limited to that whole 32 bit > + * area. > */ > ZONE_DMA32, Maybe just say various architectures instead of mentioning specific ones? Something like "Some 64-bit platforms need.."