From nobody Tue Apr 28 10:28:13 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D24B9C433EF for ; Wed, 1 Jun 2022 15:38:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351279AbiFAPiH (ORCPT ); Wed, 1 Jun 2022 11:38:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355740AbiFAPh7 (ORCPT ); Wed, 1 Jun 2022 11:37:59 -0400 Received: from mx1.uni-rostock.de (mx1.uni-rostock.de [139.30.22.71]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C17331506 for ; Wed, 1 Jun 2022 08:37:53 -0700 (PDT) DKIM-Signature: v=1; c=relaxed/relaxed; d=uni-rostock.de; s=itmze; t=1654097871; bh=PKtd8/u8nWjPZdGzm0jz3lmh4Yz0PlPqWAloSXTo6Z8=; h= "Subject:Subject:From:From:Date:Date:ReplyTo:ReplyTo:Cc:Cc:Message-Id:Message-Id"; a=ed25519-sha256; b= 6kfXov/hiy58kWFWjSHXhI4vNABC6bffFqWOsJcg+b0W5QH9j9HjLZDfk+BvG5FaI6cSSPkz44NybJcB3Lk7CA== DKIM-Signature: v=1; c=relaxed/relaxed; d=uni-rostock.de; s=itmz; t=1654097871; bh=PKtd8/u8nWjPZdGzm0jz3lmh4Yz0PlPqWAloSXTo6Z8=; h= "Subject:Subject:From:From:Date:Date:ReplyTo:ReplyTo:Cc:Cc:Message-Id:Message-Id"; a=rsa-sha256; b= anI+lOJGOjXGhC67isOqDl7m7OBz99DhbhX0eZJv5RGWxX7l1CiI3okmtAhaQAP29mPm1D3CBL60qkag43ZO+lyHZpUXHdLd6ya4Dlkz+ylavx2Q1Pvl5rzPakRXe25wYsFcqa2r9aPdxhz1ash3anJdeTmyqEkzl2/DJGkidyA= Received: from 139.30.22.81 by mx1.uni-rostock.de (Tls12, Aes256, Sha384, DiffieHellmanEllipticKey384); Wed, 01 Jun 2022 15:37:51 GMT Received: from meshdev.amd.e-technik.uni-rostock.de (139.30.202.94) by email1.uni-rostock.de (139.30.22.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.9; Wed, 1 Jun 2022 17:37:50 +0200 From: Benjamin Beichler To: , Richard Weinberger , Anton Ivanov , Johannes Berg CC: Benjamin Beichler , Johannes Berg , , Subject: [PATCH] um: read multiple msg from virtio slave request fd Date: Wed, 1 Jun 2022 15:37:22 +0000 Message-ID: <20220601153722.181427-1-benjamin.beichler@uni-rostock.de> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [139.30.202.94] X-ClientProxiedBy: EMAIL2.uni-rostock.de (139.30.22.82) To email1.uni-rostock.de (139.30.22.81) X-TM-SNTS-SMTP: 65432843B81598EC2F6963A9BD00A45E17CF9588109DE9673455B75DF549C1F72002:8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" If VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS is activated, the user mode linux virtio irq handler only read one msg from the corresponding socket. This creates issues, when the device emulation creates multiple call requests (e.g. for multiple virtqueues), as the socket buffer tend to fill up and the call requests are delayed. This creates a deadlock situation, when the device simulation blocks, because of sending a msg and the kernel side blocks because of synchronously waiting for an acknowledge of kick request. Actually inband notifications are meant to be used in combination with the time travel protocol, but it is not required, therefore this corner case needs to be handled. Anyways, in general it seems to be more natural to consume always all messages from a socket, instead of only a single one. Fixes: 2cd097ba8c05 ("um: virtio: Implement VHOST_USER_PROTOCOL_F_SLAVE_REQ= ") Signed-off-by: Benjamin Beichler --- arch/um/drivers/virtio_uml.c | 72 ++++++++++++++++++------------------ 1 file changed, 37 insertions(+), 35 deletions(-) diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c index ba562d68dc04..0c171dd11414 100644 --- a/arch/um/drivers/virtio_uml.c +++ b/arch/um/drivers/virtio_uml.c @@ -363,45 +363,47 @@ static irqreturn_t vu_req_read_message(struct virtio_= uml_device *vu_dev, struct vhost_user_msg msg; u8 extra_payload[512]; } msg; - int rc; - - rc =3D vhost_user_recv_req(vu_dev, &msg.msg, - sizeof(msg.msg.payload) + - sizeof(msg.extra_payload)); - - if (rc) - return IRQ_NONE; - - switch (msg.msg.header.request) { - case VHOST_USER_SLAVE_CONFIG_CHANGE_MSG: - vu_dev->config_changed_irq =3D true; - response =3D 0; - break; - case VHOST_USER_SLAVE_VRING_CALL: - virtio_device_for_each_vq((&vu_dev->vdev), vq) { - if (vq->index =3D=3D msg.msg.payload.vring_state.index) { - response =3D 0; - vu_dev->vq_irq_vq_map |=3D BIT_ULL(vq->index); - break; + irqreturn_t rc =3D IRQ_NONE; + + while (1) { + if (vhost_user_recv_req(vu_dev, &msg.msg, + sizeof(msg.msg.payload) + + sizeof(msg.extra_payload))) + break; + + switch (msg.msg.header.request) { + case VHOST_USER_SLAVE_CONFIG_CHANGE_MSG: + vu_dev->config_changed_irq =3D true; + response =3D 0; + break; + case VHOST_USER_SLAVE_VRING_CALL: + virtio_device_for_each_vq((&vu_dev->vdev), vq) { + if (vq->index =3D=3D + msg.msg.payload.vring_state.index) { + response =3D 0; + vu_dev->vq_irq_vq_map |=3D + BIT_ULL(vq->index); + break; + } } + break; + case VHOST_USER_SLAVE_IOTLB_MSG: + /* not supported - VIRTIO_F_ACCESS_PLATFORM */ + case VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG: + /* not supported - VHOST_USER_PROTOCOL_F_HOST_NOTIFIER */ + default: + vu_err(vu_dev, "unexpected slave request %d\n", + msg.msg.header.request); } - break; - case VHOST_USER_SLAVE_IOTLB_MSG: - /* not supported - VIRTIO_F_ACCESS_PLATFORM */ - case VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG: - /* not supported - VHOST_USER_PROTOCOL_F_HOST_NOTIFIER */ - default: - vu_err(vu_dev, "unexpected slave request %d\n", - msg.msg.header.request); - } - - if (ev && !vu_dev->suspended) - time_travel_add_irq_event(ev); =20 - if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY) - vhost_user_reply(vu_dev, &msg.msg, response); + if (ev && !vu_dev->suspended) + time_travel_add_irq_event(ev); =20 - return IRQ_HANDLED; + if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY) + vhost_user_reply(vu_dev, &msg.msg, response); + rc =3D IRQ_HANDLED; + } + return rc; } =20 static irqreturn_t vu_req_interrupt(int irq, void *data) --=20 2.25.1