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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 5D84DC43387 for ; Thu, 3 Jan 2019 16:28:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 37D4D20815 for ; Thu, 3 Jan 2019 16:28:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732250AbfACQ2e (ORCPT ); Thu, 3 Jan 2019 11:28:34 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58046 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730795AbfACQ2c (ORCPT ); Thu, 3 Jan 2019 11:28:32 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id BF5E319C301; Thu, 3 Jan 2019 16:28:32 +0000 (UTC) Received: from redhat.com (ovpn-120-148.rdu2.redhat.com [10.10.120.148]) by smtp.corp.redhat.com (Postfix) with SMTP id C21DF1001F3C; Thu, 3 Jan 2019 16:28:28 +0000 (UTC) Date: Thu, 3 Jan 2019 11:28:28 -0500 From: "Michael S. Tsirkin" To: Cornelia Huck Cc: Jason Wang , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, virtio-dev@lists.oasis-open.org, Wei Wang , Halil Pasic Subject: Re: [PATCH 2/2] virtio: document virtio_config_ops restrictions Message-ID: <20190103112627-mutt-send-email-mst@kernel.org> References: <20190103160804.21438-1-cohuck@redhat.com> <20190103160804.21438-3-cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190103160804.21438-3-cohuck@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 03 Jan 2019 16:28:32 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 03, 2019 at 05:08:04PM +0100, Cornelia Huck wrote: > Some transports (e.g. virtio-ccw) implement virtio operations that > seem to be a simple read/write as something more involved that > cannot be done from an atomic context. > > Give at least a hint about that. > > Signed-off-by: Cornelia Huck > --- > include/linux/virtio_config.h | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h > index 7087ef946ba7..987b6491b946 100644 > --- a/include/linux/virtio_config.h > +++ b/include/linux/virtio_config.h > @@ -12,6 +12,11 @@ struct irq_affinity; > > /** > * virtio_config_ops - operations for configuring a virtio device > + * Note: Do not assume that a transport implements all of the operations > + * getting/setting a value as a simple read/write! Generally speaking, > + * any of @get/@set, @get_status/@set_status, or @get_features/ > + * @finalize_features are NOT safe to be called from an atomic > + * context. > * @get: read the value of a configuration field > * vdev: the virtio_device > * offset: the offset of the configuration field Then might_sleep in virtio_cread/virtio_cwrite and friends would be appropriate? I guess we'll need to fix balloon first. > -- > 2.17.2