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=-2.4 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, 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 53AF8C46471 for ; Tue, 7 Aug 2018 06:18:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0766221A12 for ; Tue, 7 Aug 2018 06:18:23 +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="lnHFra/+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0766221A12 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 S2388554AbeHGIbF (ORCPT ); Tue, 7 Aug 2018 04:31:05 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:38450 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387588AbeHGIbF (ORCPT ); Tue, 7 Aug 2018 04:31:05 -0400 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=JL9sovPWEf8yrTpdq2Lic9cCDW4790FNP2sPj3/GabA=; b=lnHFra/+rUwS8DqHhhjF7tAKm JOtWOrWeL0UCodvEcbomlKlNOSZFan1tnMyXwY7LZ/BsPACnboETyYBOWMGx+AYuXLi5AIaiQc2Rl 3QJv6NhvuIiQdz8eaTzcIaMi9hyMMThha65U6O5fcPwkvelibQcaGJ3JtiRfyGfWE235mzbrvES5K 0whBpc3gjZ3E1FDs93yDPpcpOqvp6tMCg0rBFp8I/mDWtT9Mh8txhVUxW8ej6ozEn+9SO3FuiAxql Ct2DzyOnpPUAYv42gZ1WAC7nVRx5vMnSTk3gWFVONnMm+kHbVu2k05/Lh3xILPNxtOBqZiawm00BU P6qWl5e4A==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1fmvJv-0003TB-48; Tue, 07 Aug 2018 06:18:15 +0000 Date: Mon, 6 Aug 2018 23:18:14 -0700 From: Christoph Hellwig To: "Michael S. Tsirkin" Cc: Benjamin Herrenschmidt , Christoph Hellwig , Will Deacon , Anshuman Khandual , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, aik@ozlabs.ru, robh@kernel.org, joe@perches.com, elfring@users.sourceforge.net, david@gibson.dropbear.id.au, jasowang@redhat.com, mpe@ellerman.id.au, linuxram@us.ibm.com, haren@linux.vnet.ibm.com, paulus@samba.org, srikar@linux.vnet.ibm.com, robin.murphy@arm.com, jean-philippe.brucker@arm.com, marc.zyngier@arm.com Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices Message-ID: <20180807061814.GC32709@infradead.org> References: <20180803220443-mutt-send-email-mst@kernel.org> <051fd78e15595b414839fa8f9d445b9f4d7576c6.camel@kernel.crashing.org> <20180805031046-mutt-send-email-mst@kernel.org> <20180806164106-mutt-send-email-mst@kernel.org> <20180806233024-mutt-send-email-mst@kernel.org> <0967fc30001323e6e38ed12c8dba8ee3d1aa13f5.camel@kernel.crashing.org> <20180807002857-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180807002857-mutt-send-email-mst@kernel.org> 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, Aug 07, 2018 at 12:46:34AM +0300, Michael S. Tsirkin wrote: > Well we have the RFC for that - the switch to using DMA ops unconditionally isn't > problematic itself IMHO, for now that RFC is blocked > by its perfromance overhead for now but Christoph says > he's trying to remove that for direct mappings, > so we should hopefully be able to get there in X weeks. The direct calls to dma_direct_ops aren't going to help you with legacy virtio, given that virtio is specified to deal with physical addresses, while dma-direct is not in many cases. It would however help with the case where qemu always sets the platform dma flag, as we'd avoid the indirect calls for that.