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=-0.6 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,T_DKIM_INVALID autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id AC546C004E4 for ; Wed, 13 Jun 2018 07:41:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D874208B0 for ; Wed, 13 Jun 2018 07:41:54 +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="Fm5olaNB" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5D874208B0 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 S934610AbeFMHlw (ORCPT ); Wed, 13 Jun 2018 03:41:52 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:47882 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754476AbeFMHlu (ORCPT ); Wed, 13 Jun 2018 03:41:50 -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=oohRmM6XIpwCupB6S6+SVaE2yvOq+ENRUZwzW+aYdzI=; b=Fm5olaNB4WseSDN76h0KPd4ey OMa1qq7Wef/kJM7pMgld3a7URE+YER+MzAKgpp5GxXeUiFZ8++ro6Zb8UYsGyaoXDp8RDI6HeZu+Y XMIkAJqxp4i7Nmc27tzhGv2FN2IH1fzyHKnhDEJUUMxxR/qRX3rJtFC8wdZzcOjPrDQD7qWX2BKXa gb7MeCIkIa/wziAms6lKLqQ5M4QCIklvK2sjwheO5yEkEADHDB28sy3YTdUNMGr9XbtcVKX8dtLxc KuBX+UV2/eXEQOEXKAADGxOyVoFScS79vIcrrx73tR0syqb1qnq79hgjM0rFA4TotFNoIsy8e9qV6 llHZHkI9w==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1fT0PW-0006Yd-4h; Wed, 13 Jun 2018 07:41:42 +0000 Date: Wed, 13 Jun 2018 00:41:41 -0700 From: Christoph Hellwig To: Benjamin Herrenschmidt Cc: Ram Pai , "Michael S. Tsirkin" , Christoph Hellwig , robh@kernel.org, pawel.moll@arm.com, Tom Lendacky , aik@ozlabs.ru, jasowang@redhat.com, cohuck@redhat.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, joe@perches.com, "Rustad, Mark D" , david@gibson.dropbear.id.au, linuxppc-dev@lists.ozlabs.org, elfring@users.sourceforge.net, Anshuman Khandual Subject: Re: [RFC V2] virtio: Add platform specific DMA API translation for virito devices Message-ID: <20180613074141.GA12033@infradead.org> References: <20180522063317.20956-1-khandual@linux.vnet.ibm.com> <20180523213703-mutt-send-email-mst@kernel.org> <20180524072104.GD6139@ram.oc3035372033.ibm.com> <0c508eb2-08df-3f76-c260-90cf7137af80@linux.vnet.ibm.com> <20180531204320-mutt-send-email-mst@kernel.org> <20180607052306.GA1532@infradead.org> <20180607185234-mutt-send-email-mst@kernel.org> <20180611023909.GA5726@ram.oc3035372033.ibm.com> <07b804fccd7373c650be79ac9fa77ae7f2375ced.camel@kernel.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07b804fccd7373c650be79ac9fa77ae7f2375ced.camel@kernel.crashing.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 Mon, Jun 11, 2018 at 01:29:18PM +1000, Benjamin Herrenschmidt wrote: > At the risk of repeating myself, let's just do the first pass which is > to switch virtio over to always using the DMA API in the actual data > flow code, with a hook at initialization time that replaces the DMA ops > with some home cooked "direct" ops in the case where the IOMMU flag > isn't set. > > This will be equivalent to what we have today but avoids having 2 > separate code path all over the driver. > > Then a second stage, I think, is to replace this "hook" so that the > architecture gets a say in the matter. I don't think we can actually use dma_direct_ops. It still allows architectures to override parts of the dma setup, which virtio seems to blindly assume phys == dma and not cache flushing. I think the right way forward is to either add a new VIRTIO_F_IS_PCI_DEVICE (or redefine the existing iommu flag if deemed possible). And then make sure recent qemu always sets it. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [RFC V2] virtio: Add platform specific DMA API translation for virito devices Date: Wed, 13 Jun 2018 00:41:41 -0700 Message-ID: <20180613074141.GA12033@infradead.org> References: <20180522063317.20956-1-khandual@linux.vnet.ibm.com> <20180523213703-mutt-send-email-mst@kernel.org> <20180524072104.GD6139@ram.oc3035372033.ibm.com> <0c508eb2-08df-3f76-c260-90cf7137af80@linux.vnet.ibm.com> <20180531204320-mutt-send-email-mst@kernel.org> <20180607052306.GA1532@infradead.org> <20180607185234-mutt-send-email-mst@kernel.org> <20180611023909.GA5726@ram.oc3035372033.ibm.com> <07b804fccd7373c650be79ac9fa77ae7f2375ced.camel@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <07b804fccd7373c650be79ac9fa77ae7f2375ced.camel@kernel.crashing.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Benjamin Herrenschmidt Cc: robh@kernel.org, cohuck@redhat.com, pawel.moll@arm.com, Tom Lendacky , "Michael S. Tsirkin" , Ram Pai , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Christoph Hellwig , joe@perches.com, "Rustad, Mark D" , Anshuman Khandual , linuxppc-dev@lists.ozlabs.org, elfring@users.sourceforge.net, david@gibson.dropbear.id.au List-Id: virtualization@lists.linuxfoundation.org On Mon, Jun 11, 2018 at 01:29:18PM +1000, Benjamin Herrenschmidt wrote: > At the risk of repeating myself, let's just do the first pass which is > to switch virtio over to always using the DMA API in the actual data > flow code, with a hook at initialization time that replaces the DMA ops > with some home cooked "direct" ops in the case where the IOMMU flag > isn't set. > > This will be equivalent to what we have today but avoids having 2 > separate code path all over the driver. > > Then a second stage, I think, is to replace this "hook" so that the > architecture gets a say in the matter. I don't think we can actually use dma_direct_ops. It still allows architectures to override parts of the dma setup, which virtio seems to blindly assume phys == dma and not cache flushing. I think the right way forward is to either add a new VIRTIO_F_IS_PCI_DEVICE (or redefine the existing iommu flag if deemed possible). And then make sure recent qemu always sets it.