From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: [PATCH v4 16/15] virtio-mem: Don't rely on implicit compiler padding for requests Date: Fri, 15 May 2020 12:14:02 +0200 Message-ID: <20200515101402.16597-1-david@redhat.com> References: <20200507140139.17083-1-david@redhat.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20200507140139.17083-1-david@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Michal Hocko , Andrew Morton , "Michael S . Tsirkin" , David Hildenbrand , Pankaj Gupta , teawater List-Id: virtualization@lists.linuxfoundation.org The compiler will add padding after the last member, make that explicit. The size of a request is always 24 bytes. The size of a response always 10 bytes. Add compile-time checks. Cc: "Michael S. Tsirkin" Cc: Pankaj Gupta Cc: teawater Signed-off-by: David Hildenbrand --- Something I noticed while working on the spec (which proves that writing a virtio-spec makes sense :) ). --- drivers/virtio/virtio_mem.c | 3 +++ include/uapi/linux/virtio_mem.h | 3 +++ 2 files changed, 6 insertions(+) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 9e523db3bee1..f658fe9149be 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -1770,6 +1770,9 @@ static int virtio_mem_probe(struct virtio_device *vdev) struct virtio_mem *vm; int rc = -EINVAL; + BUILD_BUG_ON(sizeof(struct virtio_mem_req) != 24); + BUILD_BUG_ON(sizeof(struct virtio_mem_resp) != 10); + vdev->priv = vm = kzalloc(sizeof(*vm), GFP_KERNEL); if (!vm) return -ENOMEM; diff --git a/include/uapi/linux/virtio_mem.h b/include/uapi/linux/virtio_mem.h index e0a9dc7397c3..a455c488a995 100644 --- a/include/uapi/linux/virtio_mem.h +++ b/include/uapi/linux/virtio_mem.h @@ -103,16 +103,19 @@ struct virtio_mem_req_plug { __virtio64 addr; __virtio16 nb_blocks; + __virtio16 padding[3]; }; struct virtio_mem_req_unplug { __virtio64 addr; __virtio16 nb_blocks; + __virtio16 padding[3]; }; struct virtio_mem_req_state { __virtio64 addr; __virtio16 nb_blocks; + __virtio16 padding[3]; }; struct virtio_mem_req { -- 2.25.4