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 B0B82C169C4 for ; Thu, 31 Jan 2019 15:28:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 87EE22085B for ; Thu, 31 Jan 2019 15:28:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731630AbfAaP16 (ORCPT ); Thu, 31 Jan 2019 10:27:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53316 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726060AbfAaP16 (ORCPT ); Thu, 31 Jan 2019 10:27:58 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 67482804EC; Thu, 31 Jan 2019 15:27:57 +0000 (UTC) Received: from redhat.com (ovpn-124-197.rdu2.redhat.com [10.10.124.197]) by smtp.corp.redhat.com (Postfix) with SMTP id 0B90A19C7B; Thu, 31 Jan 2019 15:27:53 +0000 (UTC) Date: Thu, 31 Jan 2019 10:27:53 -0500 From: "Michael S. Tsirkin" To: Cornelia Huck Cc: Jason Wang , Halil Pasic , linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] virtio: hint if callbacks surprisingly might sleep Message-ID: <20190131102713-mutt-send-email-mst@kernel.org> References: <20190131125314.29647-1-cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190131125314.29647-1-cohuck@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Thu, 31 Jan 2019 15:27:57 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 31, 2019 at 01:53:14PM +0100, Cornelia Huck wrote: > A virtio transport is free to implement some of the callbacks in > virtio_config_ops in a matter that they cannot be called from > atomic context (e.g. virtio-ccw, which maps a lot of the callbacks > to channel I/O, which is an inherently asynchronous mechanism). > This can be very surprising for developers using the much more > common virtio-pci transport, just to find out that things break > when used on s390. > > The documentation for virtio_config_ops now contains a comment > explaining this, but it makes sense to add a might_sleep() annotation > to various wrapper functions in the virtio core to avoid surprises > later. > > Note that annotations are NOT added to two classes of calls: > - direct calls from device drivers (all current callers should be > fine, however) > - calls which clearly won't be made from atomic context (such as > those ultimately coming in via the driver core) > > Signed-off-by: Cornelia Huck Makes sense to me. I don't think we should push our luck in this release though, better defer until the merge window. > --- > > I think it is safe to add this now that the issues with the balloon > have been fixed. > > Note that this is not bulletproof (nor is it inteded to be). The > intention is to make it easier for people to catch problems earlier. > > --- > drivers/virtio/virtio.c | 2 ++ > include/linux/virtio_config.h | 13 +++++++++++++ > 2 files changed, 15 insertions(+) > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index 59e36ef4920f..98b30f54342c 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -161,6 +161,7 @@ EXPORT_SYMBOL_GPL(virtio_config_enable); > > void virtio_add_status(struct virtio_device *dev, unsigned int status) > { > + might_sleep(); > dev->config->set_status(dev, dev->config->get_status(dev) | status); > } > EXPORT_SYMBOL_GPL(virtio_add_status); > @@ -170,6 +171,7 @@ int virtio_finalize_features(struct virtio_device *dev) > int ret = dev->config->finalize_features(dev); > unsigned status; > > + might_sleep(); > if (ret) > return ret; > > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h > index 987b6491b946..bb4cc4910750 100644 > --- a/include/linux/virtio_config.h > +++ b/include/linux/virtio_config.h > @@ -290,6 +290,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val) > /* Config space accessors. */ > #define virtio_cread(vdev, structname, member, ptr) \ > do { \ > + might_sleep(); \ > /* Must match the member's type, and be integer */ \ > if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \ > (*ptr) = 1; \ > @@ -319,6 +320,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val) > /* Config space accessors. */ > #define virtio_cwrite(vdev, structname, member, ptr) \ > do { \ > + might_sleep(); \ > /* Must match the member's type, and be integer */ \ > if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \ > BUG_ON((*ptr) == 1); \ > @@ -358,6 +360,7 @@ static inline void __virtio_cread_many(struct virtio_device *vdev, > vdev->config->generation(vdev) : 0; > int i; > > + might_sleep(); > do { > old = gen; > > @@ -380,6 +383,8 @@ static inline void virtio_cread_bytes(struct virtio_device *vdev, > static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset) > { > u8 ret; > + > + might_sleep(); > vdev->config->get(vdev, offset, &ret, sizeof(ret)); > return ret; > } > @@ -387,6 +392,7 @@ static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset) > static inline void virtio_cwrite8(struct virtio_device *vdev, > unsigned int offset, u8 val) > { > + might_sleep(); > vdev->config->set(vdev, offset, &val, sizeof(val)); > } > > @@ -394,6 +400,8 @@ static inline u16 virtio_cread16(struct virtio_device *vdev, > unsigned int offset) > { > u16 ret; > + > + might_sleep(); > vdev->config->get(vdev, offset, &ret, sizeof(ret)); > return virtio16_to_cpu(vdev, (__force __virtio16)ret); > } > @@ -401,6 +409,7 @@ static inline u16 virtio_cread16(struct virtio_device *vdev, > static inline void virtio_cwrite16(struct virtio_device *vdev, > unsigned int offset, u16 val) > { > + might_sleep(); > val = (__force u16)cpu_to_virtio16(vdev, val); > vdev->config->set(vdev, offset, &val, sizeof(val)); > } > @@ -409,6 +418,8 @@ static inline u32 virtio_cread32(struct virtio_device *vdev, > unsigned int offset) > { > u32 ret; > + > + might_sleep(); > vdev->config->get(vdev, offset, &ret, sizeof(ret)); > return virtio32_to_cpu(vdev, (__force __virtio32)ret); > } > @@ -416,6 +427,7 @@ static inline u32 virtio_cread32(struct virtio_device *vdev, > static inline void virtio_cwrite32(struct virtio_device *vdev, > unsigned int offset, u32 val) > { > + might_sleep(); > val = (__force u32)cpu_to_virtio32(vdev, val); > vdev->config->set(vdev, offset, &val, sizeof(val)); > } > @@ -431,6 +443,7 @@ static inline u64 virtio_cread64(struct virtio_device *vdev, > static inline void virtio_cwrite64(struct virtio_device *vdev, > unsigned int offset, u64 val) > { > + might_sleep(); > val = (__force u64)cpu_to_virtio64(vdev, val); > vdev->config->set(vdev, offset, &val, sizeof(val)); > } > -- > 2.17.2