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=-5.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 7595BC433E1 for ; Wed, 15 Jul 2020 17:06:05 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3C23E2065F for ; Wed, 15 Jul 2020 17:06:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="CBPLDZ0a" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3C23E2065F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id 3C8248AEA7; Wed, 15 Jul 2020 17:06:04 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id w+VKKtrZigoF; Wed, 15 Jul 2020 17:06:03 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by hemlock.osuosl.org (Postfix) with ESMTP id 517E78AEA2; Wed, 15 Jul 2020 17:06:03 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 3226FC07FF; Wed, 15 Jul 2020 17:06:03 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5E763C0733; Wed, 15 Jul 2020 17:06:02 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 4C9098891B; Wed, 15 Jul 2020 17:06:02 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 7VxAeuq8vaYs; Wed, 15 Jul 2020 17:06:01 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by fraxinus.osuosl.org (Postfix) with ESMTPS id BAAD18890F; Wed, 15 Jul 2020 17:06:01 +0000 (UTC) Received: from localhost (c-67-164-102-47.hsd1.ca.comcast.net [67.164.102.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 0D53F2065E; Wed, 15 Jul 2020 17:06:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1594832761; bh=MVQs60eyaseKttygMi5Okmio5UqpxovjpBaGYM2KopU=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=CBPLDZ0a2kofL5+ir7rsYDlbbpzpSFpGzRjY5GXtgxKoOkAVo9rx/IXw2nZaAg6FP 0PGoTpRFSOeEWLcCxLE4J3D3xFoVDU+sXxptoew5BleNGM0IN0YcxXbu+SlhudGRTe VCtmQZUU53N6u7CQ+nguMHVqQdrr4STCBfllpVWM= Date: Wed, 15 Jul 2020 10:06:00 -0700 (PDT) From: Stefano Stabellini X-X-Sender: sstabellini@sstabellini-ThinkPad-T480s To: "Michael S. Tsirkin" Subject: Re: [PATCH] xen: introduce xen_vring_use_dma In-Reply-To: <20200711144334-mutt-send-email-mst@kernel.org> Message-ID: References: <20200624163940-mutt-send-email-mst@kernel.org> <20200624181026-mutt-send-email-mst@kernel.org> <20200626110629-mutt-send-email-mst@kernel.org> <20200701133456.GA23888@infradead.org> <20200701172219-mutt-send-email-mst@kernel.org> <20200711144334-mutt-send-email-mst@kernel.org> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Cc: jgross@suse.com, Peng Fan , Stefano Stabellini , konrad.wilk@oracle.com, jasowang@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Christoph Hellwig , iommu@lists.linux-foundation.org, linux-imx@nxp.com, xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com, linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Sat, 11 Jul 2020, Michael S. Tsirkin wrote: > On Fri, Jul 10, 2020 at 10:23:22AM -0700, Stefano Stabellini wrote: > > Sorry for the late reply -- a couple of conferences kept me busy. > > > > > > On Wed, 1 Jul 2020, Michael S. Tsirkin wrote: > > > On Wed, Jul 01, 2020 at 10:34:53AM -0700, Stefano Stabellini wrote: > > > > Would you be in favor of a more flexible check along the lines of the > > > > one proposed in the patch that started this thread: > > > > > > > > if (xen_vring_use_dma()) > > > > return true; > > > > > > > > > > > > xen_vring_use_dma would be implemented so that it returns true when > > > > xen_swiotlb is required and false otherwise. > > > > > > Just to stress - with a patch like this virtio can *still* use DMA API > > > if PLATFORM_ACCESS is set. So if DMA API is broken on some platforms > > > as you seem to be saying, you guys should fix it before doing something > > > like this.. > > > > Yes, DMA API is broken with some interfaces (specifically: rpmesg and > > trusty), but for them PLATFORM_ACCESS is never set. That is why the > > errors weren't reported before. Xen special case aside, there is no > > problem under normal circumstances. > > So why not fix DMA API? Then this patch is not needed. It looks like the conversation is going in circles :-) I tried to explain the reason why, even if we fixed the DMA API to work with rpmesg and trusty, we still need this patch with the following email: https://marc.info/?l=linux-kernel&m=159347446709625&w=2 At that time it looked like you agreed that we needed to improve this check? (https://marc.info/?l=linux-kernel&m=159363662418250&w=2) _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu