From nobody Thu Dec 18 01:37:30 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 389EB239E76 for ; Sat, 31 May 2025 09:52:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748685130; cv=none; b=Vf6GB5A5sWBbIwfPZZ/6Fs+HeP2lk6Zoc41AN0ji7T2AzMBoecE4QLQpJuNS6JyLHMUXKxyZoRrs4NqpunCz97qVv9nOqUlbM0C5xnVDztfiWxRilvkE4wi1VsdVGeCvIi5QRoK6Sx1+b6bgPbT5k+/Jtr00hWg3/g0syVQbWMs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748685130; c=relaxed/simple; bh=tkHlihPALOeP3kvL2nF1g8VsHMqRk4StgVF01L5qPkY=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kZezbZXwpUFde9STYEBn/Eyk5UnEXFqeyda8V1Q7znlFohfgT7YrlRdJYPXTlgl2xFcwwddxs+ULhU1oCW2m8z8iXm+buysyfYGgtG4jNpQPbaeSKY4ENbPgj6sszpIvBQir+JDAyf97cagGqAYjsMXnp/90/uLYtX1eyPftPPg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=WLHmrI1V; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WLHmrI1V" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1748685128; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bXrAvthADTqvlMjxkG4TzthDrm10AjntmLRtuzulA0I=; b=WLHmrI1V4BtXZLZBXuLq+xqtyb4nASOQpL7le00yRXrhTi7ILYFBuFd5juTN//xWQLPin6 HfuwGtvmqjKqEDY/EweEQI90w7ZJHG/0ddhhYiqa5JJcF2eDSpQi6dviaRcCdllgNkXgQQ BV3CfeSy2xuXYDlp95sgwGBUHOBxvFk= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-321-krvCGQXNNWKTxc34OjevJg-1; Sat, 31 May 2025 05:52:04 -0400 X-MC-Unique: krvCGQXNNWKTxc34OjevJg-1 X-Mimecast-MFC-AGG-ID: krvCGQXNNWKTxc34OjevJg_1748685123 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5E5F81956089; Sat, 31 May 2025 09:52:03 +0000 (UTC) Received: from server.redhat.com (unknown [10.72.112.30]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 590BF1800371; Sat, 31 May 2025 09:51:58 +0000 (UTC) From: Cindy Lu To: lulu@redhat.com, jasowang@redhat.com, mst@redhat.com, michael.christie@oracle.com, sgarzare@redhat.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org Subject: [PATCH v10 3/3] vhost: Add new UAPI to select kthread mode and KConfig to enable this IOCTL Date: Sat, 31 May 2025 17:47:05 +0800 Message-ID: <20250531095135.159582-4-lulu@redhat.com> In-Reply-To: <20250531095135.159582-1-lulu@redhat.com> References: <20250531095135.159582-1-lulu@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Content-Type: text/plain; charset="utf-8" This patch introduces a new UAPI that allows the vhost device to select in kthread mode. Userspace applications can utilize IOCTL VHOST_FORK_FROM_OWNER to select between task and kthread modes, which must be invoked before IOCTL VHOST_SET_OWNER, as the worker will be created during that call. The VHOST_NEW_WORKER requires the inherit_owner setting to be true, and a check has been added to ensure proper configuration. Additionally, a new KConfig option, CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL, is introduced to control the availability of the IOCTL VHOST_FORK_FROM_OWNER. When CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL is set to n, the IOCTL is disabled, and any attempt to use it will result in a failure. Signed-off-by: Cindy Lu --- drivers/vhost/Kconfig | 13 +++++++++++++ drivers/vhost/vhost.c | 30 +++++++++++++++++++++++++++++- include/uapi/linux/vhost.h | 16 ++++++++++++++++ 3 files changed, 58 insertions(+), 1 deletion(-) diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig index 020d4fbb947c..300e474b60fd 100644 --- a/drivers/vhost/Kconfig +++ b/drivers/vhost/Kconfig @@ -96,3 +96,16 @@ config VHOST_CROSS_ENDIAN_LEGACY If unsure, say "N". =20 endif + +config VHOST_ENABLE_FORK_OWNER_IOCTL + bool "Enable IOCTL VHOST_FORK_FROM_OWNER" + default n + help + This option enables the IOCTL VHOST_FORK_FROM_OWNER, allowing + userspace applications to modify the thread mode for vhost devices. + + By default, `CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL` is set to `n`, + which disables the IOCTL. When enabled (y), the IOCTL allows + users to set the mode as needed. + + If unsure, say "N". diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 2d2909be1bb2..673c2dc8607b 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1022,6 +1022,13 @@ long vhost_worker_ioctl(struct vhost_dev *dev, unsig= ned int ioctl, switch (ioctl) { /* dev worker ioctls */ case VHOST_NEW_WORKER: + /* + * vhost_tasks will account for worker threads under the parent's + * NPROC value but kthreads do not. To avoid userspace overflowing + * the system with worker threads inherit_owner must be true. + */ + if (!dev->inherit_owner) + return -EFAULT; ret =3D vhost_new_worker(dev, &state); if (!ret && copy_to_user(argp, &state, sizeof(state))) ret =3D -EFAULT; @@ -1138,7 +1145,7 @@ void vhost_dev_reset_owner(struct vhost_dev *dev, str= uct vhost_iotlb *umem) int i; =20 vhost_dev_cleanup(dev); - + dev->inherit_owner =3D true; dev->umem =3D umem; /* We don't need VQ locks below since vhost_dev_cleanup makes sure * VQs aren't running. @@ -2292,6 +2299,27 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned i= nt ioctl, void __user *argp) goto done; } =20 +#ifdef CONFIG_VHOST_ENABLE_FORK_OWNER_IOCTL + if (ioctl =3D=3D VHOST_FORK_FROM_OWNER) { + u8 inherit_owner; + /*inherit_owner can only be modified before owner is set*/ + if (vhost_dev_has_owner(d)) { + r =3D -EBUSY; + goto done; + } + if (copy_from_user(&inherit_owner, argp, sizeof(u8))) { + r =3D -EFAULT; + goto done; + } + if (inherit_owner > 1) { + r =3D -EINVAL; + goto done; + } + d->inherit_owner =3D (bool)inherit_owner; + r =3D 0; + goto done; + } +#endif /* You must be the owner to do anything else */ r =3D vhost_dev_check_owner(d); if (r) diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h index d4b3e2ae1314..d2692c7ef450 100644 --- a/include/uapi/linux/vhost.h +++ b/include/uapi/linux/vhost.h @@ -235,4 +235,20 @@ */ #define VHOST_VDPA_GET_VRING_SIZE _IOWR(VHOST_VIRTIO, 0x82, \ struct vhost_vring_state) + +/** + * VHOST_FORK_FROM_OWNER - Set the inherit_owner flag for the vhost device, + * This ioctl must called before VHOST_SET_OWNER. + * + * @param inherit_owner: An 8-bit value that determines the vhost thread m= ode + * + * When inherit_owner is set to 1(default value): + * - Vhost will create tasks similar to processes forked from the owner, + * inheriting all of the owner's attributes. + * + * When inherit_owner is set to 0: + * - Vhost will create tasks as kernel thread. + */ +#define VHOST_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, __u8) + #endif --=20 2.45.0