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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84F8EC433EF for ; Thu, 7 Oct 2021 11:53:19 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (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 30B256124A for ; Thu, 7 Oct 2021 11:53:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 30B256124A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id E87B8842A9; Thu, 7 Oct 2021 11:53:18 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id CokJkSRjvbPQ; Thu, 7 Oct 2021 11:53:18 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp1.osuosl.org (Postfix) with ESMTPS id 979B1842A5; Thu, 7 Oct 2021 11:53:17 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 55EE7C000F; Thu, 7 Oct 2021 11:53:17 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 8C401C000D for ; Thu, 7 Oct 2021 11:53:16 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 6F3A9409FA for ; Thu, 7 Oct 2021 11:53:16 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp4.osuosl.org (amavisd-new); dkim=pass (1024-bit key) header.d=redhat.com Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Wi86tgVs-Xxw for ; Thu, 7 Oct 2021 11:53:15 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by smtp4.osuosl.org (Postfix) with ESMTPS id A7DE4409F8 for ; Thu, 7 Oct 2021 11:53:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1633607594; 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: in-reply-to:in-reply-to:references:references; bh=AZvF8lHSRTx5C1gxLkoYVX71Yos23PQLi8wLibZ0710=; b=RRNO7UaWRln5krpU8DC7iMldqpMlM+58xdAVjMNZ0sx9YE6f+HKbYNIcM0XCkYPD1Cp0bK /svtFwpTgnu3XI99rJvwgD9wssytxPW7Glh6IRtuK+ggh69ezreEwoZ7KAzmwyMGKcdN8/ gERj3+v88ez60x4M7ZRQ+EtOeE8MYsQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-304-f60KTsS4N0205Zinm8Nj0g-1; Thu, 07 Oct 2021 07:52:49 -0400 X-MC-Unique: f60KTsS4N0205Zinm8Nj0g-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 985AB100CC84; Thu, 7 Oct 2021 11:52:47 +0000 (UTC) Received: from localhost (unknown [10.39.193.140]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7F47D4EC7D; Thu, 7 Oct 2021 11:52:26 +0000 (UTC) From: Cornelia Huck To: Halil Pasic , "Michael S. Tsirkin" , Jason Wang , Xie Yongji , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] virtio: write back F_VERSION_1 before validate In-Reply-To: <20211006142533.2735019-1-pasic@linux.ibm.com> Organization: Red Hat GmbH References: <20211006142533.2735019-1-pasic@linux.ibm.com> User-Agent: Notmuch/0.32.1 (https://notmuchmail.org) Date: Thu, 07 Oct 2021 13:52:24 +0200 Message-ID: <875yu9yruv.fsf@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Cc: linux-s390@vger.kernel.org, markver@us.ibm.com, qemu-devel@nongnu.org, Raphael Norwitz , Halil Pasic , Christian Borntraeger , stefanha@redhat.com X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Wed, Oct 06 2021, Halil Pasic wrote: > The virtio specification virtio-v1.1-cs01 states: Transitional devices > MUST detect Legacy drivers by detecting that VIRTIO_F_VERSION_1 has not > been acknowledged by the driver. This is exactly what QEMU as of 6.1 > has done relying solely on VIRTIO_F_VERSION_1 for detecting that. > > However, the specification also says: driver MAY read (but MUST NOT > write) the device-specific configuration fields to check that it can > support the device before setting FEATURES_OK. Suggest to put the citations from the spec into quotes, so that they are distinguishable from the rest of the text. > > In that case, any transitional device relying solely on > VIRTIO_F_VERSION_1 for detecting legacy drivers will return data in > legacy format. In particular, this implies that it is in big endian > format for big endian guests. This naturally confuses the driver which > expects little endian in the modern mode. > > It is probably a good idea to amend the spec to clarify that > VIRTIO_F_VERSION_1 can only be relied on after the feature negotiation > is complete. However, we already have regression so let's try to address s/regression/a regression/ > it. Maybe mention what the regression is? Also mention that we use this workaround for modern on BE only? > > Signed-off-by: Halil Pasic > Fixes: 82e89ea077b9 ("virtio-blk: Add validation for block size in config space") > Fixes: fe36cbe0671e ("virtio_net: clear MTU when out of range") > Reported-by: markver@us.ibm.com > --- > drivers/virtio/virtio.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index 0a5b54034d4b..494cfecd3376 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -239,6 +239,16 @@ static int virtio_dev_probe(struct device *_d) > driver_features_legacy = driver_features; > } > > + /* > + * Some devices detect legacy solely via F_VERSION_1. Write > + * F_VERSION_1 to force LE for these when needed. "...to force LE config space accesses before FEATURES_OK for these when needed (BE)." ? > + */ > + if (drv->validate && !virtio_legacy_is_little_endian() > + && BIT_ULL(VIRTIO_F_VERSION_1) & device_features) { Nit: putting device_features first would read more naturally to me. > + dev->features = BIT_ULL(VIRTIO_F_VERSION_1); > + dev->config->finalize_features(dev); > + } > + > if (device_features & (1ULL << VIRTIO_F_VERSION_1)) > dev->features = driver_features & device_features; > else Patch LGTM. _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization