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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CFF88C433EF for ; Fri, 1 Jul 2022 09:39:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236346AbiGAJjL (ORCPT ); Fri, 1 Jul 2022 05:39:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59900 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236207AbiGAJjK (ORCPT ); Fri, 1 Jul 2022 05:39:10 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 6754C1E3DD for ; Fri, 1 Jul 2022 02:39:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1656668348; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M6jjd4ijXuXIvJJrjir19vpImb6pnScxQWCTyU/0jws=; b=LPAmb7aixWLlNHwghQIer3DV0GXscDLx+OW5I9ldUKTwjeBtv+6DYPt67SlgWb/O3bfRYX 3Y+8jJfBzN+7IcHSg4cVN4N7bWNaydxVkxXjkrmJ7lP7wwHPhZxj2GHL5SBpEmrfIAn+nA 2LyVimUfefE2qHr4YZtQHUdv6o9rhAg= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-613-6ZkHDghJPFiNz0FqY-hDxA-1; Fri, 01 Jul 2022 05:39:07 -0400 X-MC-Unique: 6ZkHDghJPFiNz0FqY-hDxA-1 Received: by mail-wm1-f72.google.com with SMTP id m20-20020a05600c4f5400b003a03aad6bdfso785838wmq.6 for ; Fri, 01 Jul 2022 02:39:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=M6jjd4ijXuXIvJJrjir19vpImb6pnScxQWCTyU/0jws=; b=sHI5qeCviyJWLj/uq09SYUwF/Nvx+3+RyPPshK/6rmSJuHbk77ymuy68QOYbIXvTXd mo5oWNpBcQ8x6Y9EUrP6dWw0zU9FlEfcdA/lgO9DWKdtWJ9jLnlWu8jegqHlDwQsM6gL tq/2fq+UR16IBgNA+UK/6nImMhsH8pfwFukMle285MI8AFlDrD5HYAmjibMITHKX5BUT 2qXEJR7qhNGiD5YbGLJ6OPzAtamyhg5LDHQK7aSWekRdF/e+WKO/77AZHucrTUA8xWNt QkffIi7rofWOosuiFRb+xEzkwmapW9U0bbwwbhWAwnASVb8y/qMqbbXShh1TIso1Z7g5 xT1w== X-Gm-Message-State: AJIora+NcjeMk1trDHve/tye00eoc3Ev2bqNICwolElHqMikUV64usZE ciyTsNp9bof6RtEP9ZNGui3OBXJ5a5hljUgqqApVyXSP3WGF9SHd/goFPnyt6aa2pvRIWWfBgUW FVmQWVhxLflTfrfEouzlGxzxdiiCiSA== X-Received: by 2002:a05:6000:a1e:b0:21b:8c8d:3cb5 with SMTP id co30-20020a0560000a1e00b0021b8c8d3cb5mr12801981wrb.372.1656668345694; Fri, 01 Jul 2022 02:39:05 -0700 (PDT) X-Google-Smtp-Source: AGRyM1tFcAXZoAaZyHfEts4V1bW0kmJ5lrttXMA/0eqVrtSgtW5wTjnCGywc6ih/h68PKIHmHWboSw== X-Received: by 2002:a05:6000:a1e:b0:21b:8c8d:3cb5 with SMTP id co30-20020a0560000a1e00b0021b8c8d3cb5mr12801952wrb.372.1656668345358; Fri, 01 Jul 2022 02:39:05 -0700 (PDT) Received: from redhat.com ([2.55.3.188]) by smtp.gmail.com with ESMTPSA id bg28-20020a05600c3c9c00b003a175bc9c17sm6267998wmb.42.2022.07.01.02.39.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Jul 2022 02:39:04 -0700 (PDT) Date: Fri, 1 Jul 2022 05:39:01 -0400 From: "Michael S. Tsirkin" To: Arnaud POULIQUEN Cc: Mathieu Poirier , Anup Patel , Bjorn Andersson , Atish Patra , Alistair Francis , Anup Patel , linux-remoteproc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rpmsg: virtio: Fix broken rpmsg_probe() Message-ID: <20220701053813-mutt-send-email-mst@kernel.org> References: <20220608171334.730739-1-apatel@ventanamicro.com> <20220629174318.GB2018382@p14s> <20220630151716-mutt-send-email-mst@kernel.org> <65d972ed-31b4-5636-86a3-dabd5f25a3be@foss.st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <65d972ed-31b4-5636-86a3-dabd5f25a3be@foss.st.com> Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@vger.kernel.org On Fri, Jul 01, 2022 at 11:00:28AM +0200, Arnaud POULIQUEN wrote: > Hello, > > On 6/30/22 21:19, Michael S. Tsirkin wrote: > > On Wed, Jun 29, 2022 at 11:43:18AM -0600, Mathieu Poirier wrote: > >> Hi Anup, > >> > >> On Wed, Jun 08, 2022 at 10:43:34PM +0530, Anup Patel wrote: > >>> The rpmsg_probe() is broken at the moment because virtqueue_add_inbuf() > >>> fails due to both virtqueues (Rx and Tx) marked as broken by the > >>> __vring_new_virtqueue() function. To solve this, virtio_device_ready() > >>> (which unbreaks queues) should be called before virtqueue_add_inbuf(). > >>> > >>> Fixes: 8b4ec69d7e09 ("virtio: harden vring IRQ") > >>> Signed-off-by: Anup Patel > >>> --- > >>> drivers/rpmsg/virtio_rpmsg_bus.c | 6 +++--- > >>> 1 file changed, 3 insertions(+), 3 deletions(-) > >>> > >>> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c > >>> index 905ac7910c98..71a64d2c7644 100644 > >>> --- a/drivers/rpmsg/virtio_rpmsg_bus.c > >>> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c > >>> @@ -929,6 +929,9 @@ static int rpmsg_probe(struct virtio_device *vdev) > >>> /* and half is dedicated for TX */ > >>> vrp->sbufs = bufs_va + total_buf_space / 2; > >>> > >>> + /* From this point on, we can notify and get callbacks. */ > >>> + virtio_device_ready(vdev); > >>> + > >> > >> Calling virtio_device_ready() here means that virtqueue_get_buf_ctx_split() can > >> potentially be called (by way of rpmsg_recv_done()), which will race with > >> virtqueue_add_inbuf(). If buffers in the virtqueue aren't available then > >> rpmsg_recv_done() will fail, potentially breaking remote processors' state > >> machines that don't expect their initial name service to fail when the "device" > >> has been marked as ready. > > > > When you say available I am guessing you really need used. > > > > With a non broken device you won't get a callback > > until some buffers have been used. > > > > Or, if no used buffers are present then you will get another > > callback down the road. > > In current implementation the Linux rpmsg_virtio driver allocates the > virtio buffers for the coprocessor rpmsg virtio device transmission and > then updates the virtio device status in shared memory to inform the > coprocessor that it is ready for inter-processor communication. > > So from coprocessor perspective, when the virtio device is ready > (set to VIRTIO_CONFIG_S_DRIVER_OK), it can > start to get available buffers and send virtio buffers to the Linux. > > With the patch proposed, the virtio is set to VIRTIO_CONFIG_S_DRIVER_OK > while no buffer are available for the coprocessor transmission. > > I'm agree that, if the Linux rpmsg_virtio driver has not allocated the > buffer, the coprocessor will fail to get available virtio buffer for > communication and so has "just" to wait that some buffers are available > in the virtqueue. > > But this change the behavior and can lead to an unexpected error case > for some legacy coprocessor firmware... > Should we take the risk that this legacy is no longer compatible? > > > That said regarding the virtio spec 1.1 chapter 3.1.1 [1], I also wonder > if the introduction of the virqueue broken flag is compliant with the > spec? > But i guess this is probably a matter of interpretation... > > " > The driver MUST follow this sequence to initialize a device: > [...] > 7. Perform device-specific setup, including discovery of virtqueues for > the device, optional per-bus setup, reading and possibly writing the > device’s virtio configuration space, and population of virtqueues. > 8. Set the DRIVER_OK status bit. At this point the device is “live”. > " > > My question is what means in point 7. "and population of virtqueues"? > > In my interpretation the call of "virtqueue_add_inbuf()" populates the > RX virtqueue. > That would mean that calling virtqueue_add_inbuf before calling > virtio_device_ready() should be possible. > > Thanks, > Arnaud > > [1]https://docs.oasis-open.org/virtio/virtio/v1.1/csprd01/virtio-v1.1-csprd01.html#x1-920001 I think I agree. For example, the networking device uses "population" in this sense: It is generally a good idea to keep the receive virtqueue as fully populated as possible: if it runs out, network performance will suffer. > > > > > > >> > >> What does make me curious though is that nobody on the remoteproc mailing list > >> has complained about commit 8b4ec69d7e09 breaking their environment... By now, > >> i.e rc4, that should have happened. Anyone from TI, ST and Xilinx care to test this on > >> their rig? > >> > >> Thanks, > >> Mathieu > >> > >>> /* set up the receive buffers */ > >>> for (i = 0; i < vrp->num_bufs / 2; i++) { > >>> struct scatterlist sg; > >>> @@ -983,9 +986,6 @@ static int rpmsg_probe(struct virtio_device *vdev) > >>> */ > >>> notify = virtqueue_kick_prepare(vrp->rvq); > >>> > >>> - /* From this point on, we can notify and get callbacks. */ > >>> - virtio_device_ready(vdev); > >>> - > >>> /* tell the remote processor it can start sending messages */ > >>> /* > >>> * this might be concurrent with callbacks, but we are only > >>> -- > >>> 2.34.1 > >>> > >> > >