From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f198.google.com (mail-qk0-f198.google.com [209.85.220.198]) by kanga.kvack.org (Postfix) with ESMTP id CD8D36B0003 for ; Fri, 27 Apr 2018 12:36:26 -0400 (EDT) Received: by mail-qk0-f198.google.com with SMTP id z128so1771360qka.8 for ; Fri, 27 Apr 2018 09:36:26 -0700 (PDT) Received: from resqmta-ch2-08v.sys.comcast.net (resqmta-ch2-08v.sys.comcast.net. [2001:558:fe21:29:69:252:207:40]) by mx.google.com with ESMTPS id v57-v6si1743093qtj.154.2018.04.27.09.36.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 Apr 2018 09:36:26 -0700 (PDT) Date: Fri, 27 Apr 2018 11:36:23 -0500 (CDT) From: Christopher Lameter Subject: Re: [LSF/MM TOPIC NOTES] x86 ZONE_DMA love In-Reply-To: <20180427161813.GD8161@bombadil.infradead.org> Message-ID: References: <20180426215406.GB27853@wotan.suse.de> <20180427053556.GB11339@infradead.org> <20180427071843.GB17484@dhcp22.suse.cz> <20180427161813.GD8161@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: Michal Hocko , Christoph Hellwig , "Luis R. Rodriguez" , linux-mm@kvack.org, Jan Kara , matthew@wil.cx, x86@kernel.org, luto@amacapital.net, martin.petersen@oracle.com, jthumshirn@suse.de, broonie@kernel.org, linux-spi@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "lsf-pc@lists.linux-foundation.org" On Fri, 27 Apr 2018, Matthew Wilcox wrote: > Some devices have incredibly bogus hardware like 28 bit addressing > or 39 bit addressing. We don't have a good way to allocate memory by > physical address other than than saying "GFP_DMA for anything less than > 32, GFP_DMA32 (or GFP_KERNEL on 32-bit) for anything less than 64 bit". > > Even CMA doesn't have a "cma_alloc_phys()". Maybe that's the right place > to put such an allocation API. The other way out of this would be to require a IOMMU?