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 X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88250C43441 for ; Wed, 28 Nov 2018 19:27:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5BB6F206B6 for ; Wed, 28 Nov 2018 19:27:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5BB6F206B6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=davemloft.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-parisc-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726478AbeK2GaB (ORCPT ); Thu, 29 Nov 2018 01:30:01 -0500 Received: from shards.monkeyblade.net ([23.128.96.9]:36922 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725772AbeK2GaB (ORCPT ); Thu, 29 Nov 2018 01:30:01 -0500 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::bf5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id B5B7814E0FF78; Wed, 28 Nov 2018 11:27:17 -0800 (PST) Date: Wed, 28 Nov 2018 11:27:17 -0800 (PST) Message-Id: <20181128.112717.149234960284639699.davem@davemloft.net> To: torvalds@linux-foundation.org Cc: linux@armlinux.org.uk, hch@lst.de, linux-arch@vger.kernel.org, linux-ia64@vger.kernel.org, linux-parisc@vger.kernel.org, robin.murphy@arm.com, x86@kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-alpha@vger.kernel.org, xen-devel@lists.xenproject.org, dwmw2@infradead.org, linux-arm-kernel@lists.infradead.org Subject: Re: remove the ->mapping_error method from dma_map_ops V2 From: David Miller In-Reply-To: References: <20181128174545.GJ30658@n2100.armlinux.org.uk> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 28 Nov 2018 11:27:18 -0800 (PST) Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org From: Linus Torvalds Date: Wed, 28 Nov 2018 10:00:06 -0800 > Not all memory is accessible even to the kernel. If you have memory > that shows up in the last page of phys_addr_t, you just mark it > reserved at boot-time. It's not the physical memory at the end that needs to be reserved. It's the IOMMU mapping arena. That basically requires changes to every IOMMU implementation in the tree. Not saying it's hard or impossible, but it is real meticulous work that needs to be done in order to realize this.