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=-12.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 59D63C433E0 for ; Wed, 3 Feb 2021 18:29:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 085D364DE1 for ; Wed, 3 Feb 2021 18:29:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232131AbhBCS3a (ORCPT ); Wed, 3 Feb 2021 13:29:30 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50718 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231166AbhBCS33 (ORCPT ); Wed, 3 Feb 2021 13:29:29 -0500 Received: from mail-ed1-x533.google.com (mail-ed1-x533.google.com [IPv6:2a00:1450:4864:20::533]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F331AC0613D6 for ; Wed, 3 Feb 2021 10:28:48 -0800 (PST) Received: by mail-ed1-x533.google.com with SMTP id g10so838286eds.2 for ; Wed, 03 Feb 2021 10:28:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=deKmDPZvxIuZwtD1VBiDKxq5DpDNT8e07XxCpE/cvT0=; b=hQVQuaI8pkqkS6L+ood4W5X3XXISXMSRVeb64JeIF1OiOmHm3hN1PXnNTa+eNomtdU k7yljb1eu//LQQBM7y4WbTbM+tyn7Xw0UEIch4M/IKBFs489HMKCV6Df7G4mSi/VrApx X2bg8yh17S1FKu077Sco/E+ZwgQLJqS/N0Psj3AVpJ4b/kRZ8rSoBoyjGp6qgFuoCzEm WijjfUbEjq0pEB8MPgoObqHatLhprPyRc7r0fA+63U5eUKCiiVsbOAplICfX37Jf7fk8 zC+lblsfgUeFShy175Jk5Vb6MwXavlJelZA/velPqAsUhwJqhfXhcLLXNt9S9KiDbQ+b 2x+Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=deKmDPZvxIuZwtD1VBiDKxq5DpDNT8e07XxCpE/cvT0=; b=YnoGT+HxZTq5rfpEszGFC9MUFgZVxPXA853cKNa28aV0thRMaYzQATicXZ+y15xX5H kQJmFYNnMsKf7zOFk+vY/wM4+ddwdbQN31ZeaTSkqOlFJfCdZVZ5raocF0fZzVM+XON1 QUVXOrnLg+fnMEtQHwgcBsQhOgKAeYs6NKXvrizjJNri41hI2jptvE4J9yVfYDvmCnp7 2jzy5W/P9wa4PFejsNsn4pxwOWl6gzTFWZ5WQMbnz358Ai9QiHfyIn1ZqfvzTxA3dbLE 0UjIrq2H+ldPA5YoENFSUjpZcJ4Gl9l/dmd1KpCMTjonPLccjRdZ6LJZTM9U4wsvmPaI lMtg== X-Gm-Message-State: AOAM533DGtiK1X5EPYRBLI/+DoLO9cPRSdxYpfMhXYk0RMigs1vh33hi /CCfsBO0JJHcjF5isTrn1nQQi4vnAkaXUOItZTg= X-Google-Smtp-Source: ABdhPJwOPfZsPY5C71OdoeodHEOHYUshG/GCcrIRNJjIbXDJNJk4/9fnLU/YytcvgbeZiYNkoUxV44likijyqs16nG4= X-Received: by 2002:a05:6402:d09:: with SMTP id eb9mr4411830edb.285.1612376927774; Wed, 03 Feb 2021 10:28:47 -0800 (PST) MIME-Version: 1.0 References: <20210129002136.70865-1-weiwan@google.com> <3a3e005d-f9b2-c16a-5ada-6e04242c618e@redhat.com> In-Reply-To: <3a3e005d-f9b2-c16a-5ada-6e04242c618e@redhat.com> From: Willem de Bruijn Date: Wed, 3 Feb 2021 13:28:11 -0500 Message-ID: Subject: Re: [PATCH net] virtio-net: suppress bad irq warning for tx napi To: Jason Wang Cc: Wei Wang , David Miller , Network Development , Jakub Kicinski , Willem de Bruijn , virtualization@lists.linux-foundation.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Feb 3, 2021 at 12:33 AM Jason Wang wrote: > > > On 2021/2/2 =E4=B8=8B=E5=8D=8810:37, Willem de Bruijn wrote: > > On Mon, Feb 1, 2021 at 10:09 PM Jason Wang wrote: > >> > >> On 2021/1/29 =E4=B8=8A=E5=8D=888:21, Wei Wang wrote: > >>> With the implementation of napi-tx in virtio driver, we clean tx > >>> descriptors from rx napi handler, for the purpose of reducing tx > >>> complete interrupts. But this could introduce a race where tx complet= e > >>> interrupt has been raised, but the handler found there is no work to = do > >>> because we have done the work in the previous rx interrupt handler. > >>> This could lead to the following warning msg: > >>> [ 3588.010778] irq 38: nobody cared (try booting with the > >>> "irqpoll" option) > >>> [ 3588.017938] CPU: 4 PID: 0 Comm: swapper/4 Not tainted > >>> 5.3.0-19-generic #20~18.04.2-Ubuntu > >>> [ 3588.017940] Call Trace: > >>> [ 3588.017942] > >>> [ 3588.017951] dump_stack+0x63/0x85 > >>> [ 3588.017953] __report_bad_irq+0x35/0xc0 > >>> [ 3588.017955] note_interrupt+0x24b/0x2a0 > >>> [ 3588.017956] handle_irq_event_percpu+0x54/0x80 > >>> [ 3588.017957] handle_irq_event+0x3b/0x60 > >>> [ 3588.017958] handle_edge_irq+0x83/0x1a0 > >>> [ 3588.017961] handle_irq+0x20/0x30 > >>> [ 3588.017964] do_IRQ+0x50/0xe0 > >>> [ 3588.017966] common_interrupt+0xf/0xf > >>> [ 3588.017966] > >>> [ 3588.017989] handlers: > >>> [ 3588.020374] [<000000001b9f1da8>] vring_interrupt > >>> [ 3588.025099] Disabling IRQ #38 > >>> > >>> This patch adds a new param to struct vring_virtqueue, and we set it = for > >>> tx virtqueues if napi-tx is enabled, to suppress the warning in such > >>> case. > >>> > >>> Fixes: 7b0411ef4aa6 ("virtio-net: clean tx descriptors from rx napi") > >>> Reported-by: Rick Jones > >>> Signed-off-by: Wei Wang > >>> Signed-off-by: Willem de Bruijn > >> > >> Please use get_maintainer.pl to make sure Michael and me were cced. > > Will do. Sorry about that. I suggested just the virtualization list, my= bad. > > > >>> --- > >>> drivers/net/virtio_net.c | 19 ++++++++++++++----- > >>> drivers/virtio/virtio_ring.c | 16 ++++++++++++++++ > >>> include/linux/virtio.h | 2 ++ > >>> 3 files changed, 32 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > >>> index 508408fbe78f..e9a3f30864e8 100644 > >>> --- a/drivers/net/virtio_net.c > >>> +++ b/drivers/net/virtio_net.c > >>> @@ -1303,13 +1303,22 @@ static void virtnet_napi_tx_enable(struct vir= tnet_info *vi, > >>> return; > >>> } > >>> > >>> + /* With napi_tx enabled, free_old_xmit_skbs() could be called f= rom > >>> + * rx napi handler. Set work_steal to suppress bad irq warning = for > >>> + * IRQ_NONE case from tx complete interrupt handler. > >>> + */ > >>> + virtqueue_set_work_steal(vq, true); > >>> + > >>> return virtnet_napi_enable(vq, napi); > >> > >> Do we need to force the ordering between steal set and napi enable? > > The warning only occurs after one hundred spurious interrupts, so not > > really. > > > Ok, so it looks like a hint. Then I wonder how much value do we need to > introduce helper like virtqueue_set_work_steal() that allows the caller > to toggle. How about disable the check forever during virtqueue > initialization? Yes, that is even simpler. We still need the helper, as the internal variables of vring_virtqueue are not accessible from virtio-net. An earlier patch added the variable to virtqueue itself, but I think it belongs in vring_virtqueue. And the helper is not a lot of code.