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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,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 5D608C83003 for ; Wed, 29 Apr 2020 03:35:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3522B206D8 for ; Wed, 29 Apr 2020 03:35:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="UF3RQFaL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726678AbgD2Dfs (ORCPT ); Tue, 28 Apr 2020 23:35:48 -0400 Received: from mail26.static.mailgun.info ([104.130.122.26]:38994 "EHLO mail26.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726551AbgD2Dfs (ORCPT ); Tue, 28 Apr 2020 23:35:48 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1588131347; h=In-Reply-To: Content-Type: MIME-Version: References: Reply-To: Message-ID: Subject: Cc: To: From: Date: Sender; bh=RKZjGjRaRWOMA4bE7u8bYNMGSYHBc1o/5aoxXJ54jnQ=; b=UF3RQFaLof+5O/hFPoKjFlz5tpUNnScnSIb9FENKdSFtxf0g/Q1Kf6gpzYvaQt3MXn9uJsoz Wvsu6560LqUM7K0+p7g1TpB7Z5sP8LXnKHItCGCooLd0odjK7oQHbOqgzBMQh65n4eA41TDl Cx1S+iOT36h2gV9PQQVQQMnLQII= X-Mailgun-Sending-Ip: 104.130.122.26 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by mxa.mailgun.org with ESMTP id 5ea8f613.7f1ff9fc10a0-smtp-out-n05; Wed, 29 Apr 2020 03:35:47 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 359A1C43637; Wed, 29 Apr 2020 03:35:47 +0000 (UTC) Received: from quicinc.com (blr-bdr-fw-01_GlobalNAT_AllZones-Outside.qualcomm.com [103.229.18.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: svaddagi) by smtp.codeaurora.org (Postfix) with ESMTPSA id 7C61BC433D2; Wed, 29 Apr 2020 03:35:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 7C61BC433D2 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=vatsa@codeaurora.org Date: Wed, 29 Apr 2020 09:05:39 +0530 From: Srivatsa Vaddagiri To: "Michael S. Tsirkin" Cc: konrad.wilk@oracle.com, jasowang@redhat.com, jan.kiszka@siemens.com, will@kernel.org, stefano.stabellini@xilinx.com, iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, virtio-dev@lists.oasis-open.org, tsoni@codeaurora.org, pratikp@codeaurora.org, christoffer.dall@arm.com, alex.bennee@linaro.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 5/5] virtio: Add bounce DMA ops Message-ID: <20200429033539.GB5097@quicinc.com> Reply-To: Srivatsa Vaddagiri References: <1588073958-1793-1-git-send-email-vatsa@codeaurora.org> <1588073958-1793-6-git-send-email-vatsa@codeaurora.org> <20200428121232-mutt-send-email-mst@kernel.org> <20200428174952.GA5097@quicinc.com> <20200428163448-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20200428163448-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Michael S. Tsirkin [2020-04-28 16:41:04]: > > Won't we still need some changes to virtio to make use of its own pool (to > > bounce buffers)? Something similar to its own DMA ops proposed in this patch? > > If you are doing this for all devices, you need to either find a way > to do this without chaning DMA ops, or by doing some automatic change > to all drivers. Ok thanks for this input. I will see how we can obfuscate this in DMA APIs itself. Can you also comment on the virtio transport problem I cited? The hypervisor we are dealing with does not support MMIO transport. It supports message queue send/recv and also doorbell, which I think can be used if we can make some change like this to virtio_mmio.c: +static inline u32 +virtio_readl(struct virtio_mmio_device *vm_dev, u32 reg_offset) +{ + return vm_dev->mmio_ops->readl(vm_dev, reg_offset); +} + +static inline void +virtio_writel(struct virtio_mmio_device *vm_dev, u32 reg_offset, u32 data) +{ + vm_dev->mmio_ops->writel(vm_dev, reg_offset, data); +} /* Check magic value */ - magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE); + magic = vrito_readl(vm_dev, VIRTIO_MMIO_MAGIC_VALUE); mmio_ops->readl on most platforms can default to readl itself, while on a platform like us, it can boil down to message_queue send/recv. Would such a change be acceptable? -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation