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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 D6326C43441 for ; Fri, 9 Nov 2018 07:45:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B9EF2086C for ; Fri, 9 Nov 2018 07:45:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="jEkC6CjS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B9EF2086C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728328AbeKIRYg (ORCPT ); Fri, 9 Nov 2018 12:24:36 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:48832 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727962AbeKIRYg (ORCPT ); Fri, 9 Nov 2018 12:24:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=NQU5as14VuxTEo4YTlnWbZyJ2D6SWiG2oqZ8giH4tNg=; b=jEkC6CjS8klVnLdIQ79D4aklT 7fSebe0x5RjlmNwm+1/6m5iWgtIfkoundoFdSUZ02ox1DY9njb9YYnCiNUSps3t6R3Hv8xW5/wlXm iATXe5jIUHChpdI5AGRj+P6+oH6RSnAXoluoCXq7E4aTD5pgEUcC9SdZfDNggkUCQfK0OV0LPrmQU opX3293wE/vDHKptX8cyzNZV2NAOnBlXnV4Vfoc1r/m/NTlFn0wDYBuj9GU6XSg5/kd5xG01Yqrbn 6dQoFdt3FcYB2R2C/pClq8wja2+OSpwNZztid4luQWt3sp1MDda3S5qAAXmmpnstqQXgdInwjB5q9 3Nx8N3ZsQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gL1Tb-0000PW-4K; Fri, 09 Nov 2018 07:45:11 +0000 Date: Thu, 8 Nov 2018 23:45:10 -0800 From: Christoph Hellwig To: Robin Murphy Cc: Christoph Hellwig , Nicolin Chen , joro@8bytes.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] iommu/dma: Zero pages manually in a length of scatterlist Message-ID: <20181109074510.GA27623@infradead.org> References: <20181101213500.21800-1-nicoleotsuka@gmail.com> <63184c22-4587-be2b-8089-d2e4e0b5482d@arm.com> <20181102233613.GA26856@Asurada-Nvidia.nvidia.com> <20181105145847.GA31337@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 06, 2018 at 02:39:26PM +0000, Robin Murphy wrote: > ...and I have some significant objections to that simplification which I > plan to respond with ;) > > (namely that it defaults the whole higher-order page allocation business > which will have varying degrees of performance impact on certain cases) Well, please place your objection there. The behavior does match what every other iommu-based dma ops implementation ouside of arm/arm64 does, so there is some precedent for it to say the least. But if the only current users objects I'll surely find a way to accomodate it, but a good rationale including numbers would be useful to document it.