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=-2.0 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 D5CF5C8300A for ; Thu, 30 Apr 2020 10:34:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1A0520838 for ; Thu, 30 Apr 2020 10:34:56 +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="Lx1tODra" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726829AbgD3Kez (ORCPT ); Thu, 30 Apr 2020 06:34:55 -0400 Received: from mail26.static.mailgun.info ([104.130.122.26]:12248 "EHLO mail26.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726309AbgD3Kez (ORCPT ); Thu, 30 Apr 2020 06:34:55 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1588242894; h=In-Reply-To: Content-Type: MIME-Version: References: Reply-To: Message-ID: Subject: Cc: To: From: Date: Sender; bh=FacaeX+QW3gZe3CsWw46u78war6rqHZGj6J6LKrNjcs=; b=Lx1tODratd2FPN/DnDoLP6n+swOCkWbIEz/z/q+bg1Yy5CvxyoiTgObDBHoE/4OQxgv++uU2 GB6NSZo9NS8sB+BowTugIt+gsV3/WTCdcRXtc5CTrR/gBMGlEm9+7EmmJI6kuj//mkWd5QX7 jFXkHUsO2ev7C+Dt39nj1ENb/4U= 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 5eaaa9ce.7f386b0530a0-smtp-out-n01; Thu, 30 Apr 2020 10:34:54 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 29249C432C2; Thu, 30 Apr 2020 10:34:54 +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 73383C433CB; Thu, 30 Apr 2020 10:34:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 73383C433CB 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: Thu, 30 Apr 2020 16:04:46 +0530 From: Srivatsa Vaddagiri To: Will Deacon Cc: konrad.wilk@oracle.com, mst@redhat.com, jasowang@redhat.com, jan.kiszka@siemens.com, 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: [RFC/PATCH 1/1] virtio: Introduce MMIO ops Message-ID: <20200430103446.GH5097@quicinc.com> Reply-To: Srivatsa Vaddagiri References: <1588240976-10213-1-git-send-email-vatsa@codeaurora.org> <1588240976-10213-2-git-send-email-vatsa@codeaurora.org> <20200430101431.GD19932@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20200430101431.GD19932@willie-the-truck> 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 * Will Deacon [2020-04-30 11:14:32]: > > +#ifdef CONFIG_VIRTIO_MMIO_OPS > > > > +static struct virtio_mmio_ops *mmio_ops; > > + > > +#define virtio_readb(a) mmio_ops->mmio_readl((a)) > > +#define virtio_readw(a) mmio_ops->mmio_readl((a)) > > +#define virtio_readl(a) mmio_ops->mmio_readl((a)) > > +#define virtio_writeb(val, a) mmio_ops->mmio_writeb((val), (a)) > > +#define virtio_writew(val, a) mmio_ops->mmio_writew((val), (a)) > > +#define virtio_writel(val, a) mmio_ops->mmio_writel((val), (a)) > > How exactly are these ops hooked up? I'm envisaging something like: > > ops = spec_compliant_ops; > [...] > if (firmware_says_hypervisor_is_buggy()) > ops = magic_qcom_ops; > > am I wrong? If CONFIG_VIRTIO_MMIO_OPS is defined, then I expect this to be unconditionally set to 'magic_qcom_ops' that uses hypervisor-supported interface for IO (for example: message_queue_send() and message_queue_recevie() hypercalls). > > +int register_virtio_mmio_ops(struct virtio_mmio_ops *ops) > > +{ > > + pr_info("Registered %s as mmio ops\n", ops->name); > > + mmio_ops = ops; > > Not looking good, and really defeats the point of standardising this stuff > imo. Ok. I guess the other option is to standardize on a new virtio transport (like ivshmem2-virtio)? -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation