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Mon, 09 Jun 2025 03:34:52 -0400 X-MC-Unique: Ez1jdxpFOfyoxJ1DxF1xyQ-1 X-Mimecast-MFC-AGG-ID: Ez1jdxpFOfyoxJ1DxF1xyQ_1749454491 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 039FB195608B; Mon, 9 Jun 2025 07:34:51 +0000 (UTC) Received: from server.redhat.com (unknown [10.72.112.22]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 2449419560AB; Mon, 9 Jun 2025 07:34:46 +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 v11 3/3] vhost: Add configuration controls for vhost worker's mode Date: Mon, 9 Jun 2025 15:33:09 +0800 Message-ID: <20250609073430.442159-4-lulu@redhat.com> In-Reply-To: <20250609073430.442159-1-lulu@redhat.com> References: <20250609073430.442159-1-lulu@redhat.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 This patch introduces functionality to control the vhost worker mode: - Add two new IOCTLs: * VHOST_SET_FORK_FROM_OWNER: Allows userspace to select between task mode (fork_owner=1) and kthread mode (fork_owner=0) * VHOST_GET_FORK_FROM_OWNER: Retrieves the current thread mode setting - Expose module parameter 'fork_from_owner_default' to allow system administrators to configure the default mode for vhost workers - Add KConfig option CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL to control the availability of these IOCTLs and parameter, allowing distributions to disable them if not needed - The VHOST_NEW_WORKER functionality requires fork_owner to be set to true, with validation added to ensure proper configuration Signed-off-by: Cindy Lu --- drivers/vhost/Kconfig | 17 +++++++++++++++ drivers/vhost/vhost.c | 44 ++++++++++++++++++++++++++++++++++++++ include/uapi/linux/vhost.h | 25 ++++++++++++++++++++++ 3 files changed, 86 insertions(+) diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig index 020d4fbb947c..49e1d9dc92b7 100644 --- a/drivers/vhost/Kconfig +++ b/drivers/vhost/Kconfig @@ -96,3 +96,20 @@ config VHOST_CROSS_ENDIAN_LEGACY If unsure, say "N". endif + +config CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL + bool "Enable CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL" + default n + help + This option enables two IOCTLs: VHOST_SET_FORK_FROM_OWNER and + VHOST_GET_FORK_FROM_OWNER. These allow userspace applications + to modify the vhost worker mode for vhost devices. + + Also expose module parameter 'fork_from_owner_default' to allow users + to configure the default mode for vhost workers. + + By default, `CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL` is set to `n`, + which disables the IOCTLs and parameter. + When enabled (y), users can change the worker thread mode as needed. + + If unsure, say "N". diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 37d3ed8be822..903d9c3f6784 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -43,6 +43,11 @@ module_param(max_iotlb_entries, int, 0444); MODULE_PARM_DESC(max_iotlb_entries, "Maximum number of iotlb entries. (default: 2048)"); static bool fork_from_owner_default = true; +#ifdef CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL +module_param(fork_from_owner_default, bool, 0444); +MODULE_PARM_DESC(fork_from_owner_default, + "Set task mode as the default(default: Y)"); +#endif enum { VHOST_MEMORY_F_LOG = 0x1, @@ -1019,6 +1024,13 @@ long vhost_worker_ioctl(struct vhost_dev *dev, unsigned 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 fork_owner must be true. + */ + if (!dev->fork_owner) + return -EFAULT; ret = vhost_new_worker(dev, &state); if (!ret && copy_to_user(argp, &state, sizeof(state))) ret = -EFAULT; @@ -1136,6 +1148,7 @@ void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_iotlb *umem) vhost_dev_cleanup(dev); + dev->fork_owner = fork_from_owner_default; dev->umem = umem; /* We don't need VQ locks below since vhost_dev_cleanup makes sure * VQs aren't running. @@ -2289,6 +2302,37 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp) goto done; } +#ifdef CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL + u8 fork_owner; + + if (ioctl == VHOST_SET_FORK_FROM_OWNER) { + /*fork_owner can only be modified before owner is set*/ + if (vhost_dev_has_owner(d)) { + r = -EBUSY; + goto done; + } + if (copy_from_user(&fork_owner, argp, sizeof(u8))) { + r = -EFAULT; + goto done; + } + if (fork_owner > 1) { + r = -EINVAL; + goto done; + } + d->fork_owner = (bool)fork_owner; + r = 0; + goto done; + } + if (ioctl == VHOST_GET_FORK_FROM_OWNER) { + fork_owner = d->fork_owner; + if (copy_to_user(argp, &fork_owner, sizeof(u8))) { + r = -EFAULT; + goto done; + } + r = 0; + goto done; + } +#endif /* You must be the owner to do anything else */ r = vhost_dev_check_owner(d); if (r) diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h index d4b3e2ae1314..e51d6a347607 100644 --- a/include/uapi/linux/vhost.h +++ b/include/uapi/linux/vhost.h @@ -235,4 +235,29 @@ */ #define VHOST_VDPA_GET_VRING_SIZE _IOWR(VHOST_VIRTIO, 0x82, \ struct vhost_vring_state) + +/** + * VHOST_SET_FORK_FROM_OWNER - Set the fork_owner flag for the vhost device, + * This ioctl must called before VHOST_SET_OWNER. + * Only available when CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL=y + * + * @param fork_owner: An 8-bit value that determines the vhost thread mode + * + * When fork_owner is set to 1(default value): + * - Vhost will create vhost worker as tasks forked from the owner, + * inheriting all of the owner's attributes. + * + * When fork_owner is set to 0: + * - Vhost will create vhost workers as kernel threads. + */ +#define VHOST_SET_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, __u8) + +/** + * VHOST_GET_FORK_OWNER - Get the current fork_owner flag for the vhost device. + * Only available when CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL=y + * + * @return: An 8-bit value indicating the current thread mode. + */ +#define VHOST_GET_FORK_FROM_OWNER _IOR(VHOST_VIRTIO, 0x84, __u8) + #endif -- 2.45.0