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 E2B94C169C4 for ; Thu, 31 Jan 2019 12:53:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA03C2086C for ; Thu, 31 Jan 2019 12:53:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733071AbfAaMx1 (ORCPT ); Thu, 31 Jan 2019 07:53:27 -0500 Received: from mx1.redhat.com ([209.132.183.28]:53292 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732386AbfAaMx0 (ORCPT ); Thu, 31 Jan 2019 07:53:26 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0C1EF88312; Thu, 31 Jan 2019 12:53:26 +0000 (UTC) Received: from localhost (ovpn-116-34.ams2.redhat.com [10.36.116.34]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8DFDE18A4D; Thu, 31 Jan 2019 12:53:23 +0000 (UTC) From: Cornelia Huck To: "Michael S . Tsirkin" , Jason Wang Cc: Halil Pasic , linux-s390@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Cornelia Huck Subject: [PATCH RFC] virtio: hint if callbacks surprisingly might sleep Date: Thu, 31 Jan 2019 13:53:14 +0100 Message-Id: <20190131125314.29647-1-cohuck@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Thu, 31 Jan 2019 12:53:26 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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