kernel/linux.git/drivers/vhost/vhost.h, branch v6.18.21

vhost: rewind next_avail_head while discarding descriptors

2025-11-26T22:44:58+00:00

When discarding descriptors with IN_ORDER, we should rewind next_avail_head otherwise it would run out of sync with last_avail_idx. This would cause driver to report "id X is not a head". Fixing this by returning the number of descriptors that is used for each buffer via vhost_get_vq_desc_n() so caller can use the value while discarding descriptors. Fixes: 67a873df0c41 ("vhost: basic in order support") Cc: stable@vger.kernel.org Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin Link: https://patch.msgid.link/20251120022950.10117-1-jasowang@redhat.com Signed-off-by: Jakub Kicinski

Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

2025-08-01T21:17:48+00:00

Pull virtio updates from Michael Tsirkin: - vhost can now support legacy threading if enabled in Kconfig - vsock memory allocation strategies for large buffers have been improved, reducing pressure on kmalloc - vhost now supports the in-order feature. guest bits missed the merge window. - fixes, cleanups all over the place * tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost: (30 commits) vsock/virtio: Allocate nonlinear SKBs for handling large transmit buffers vsock/virtio: Rename virtio_vsock_skb_rx_put() vhost/vsock: Allocate nonlinear SKBs for handling large receive buffers vsock/virtio: Move SKB allocation lower-bound check to callers vsock/virtio: Rename virtio_vsock_alloc_skb() vsock/virtio: Resize receive buffers so that each SKB fits in a 4K page vsock/virtio: Move length check to callers of virtio_vsock_skb_rx_put() vsock/virtio: Validate length in packet header before skb_put() vhost/vsock: Avoid allocating arbitrarily-sized SKBs vhost_net: basic in_order support vhost: basic in order support vhost: fail early when __vhost_add_used() fails vhost: Reintroduce kthread API and add mode selection vdpa: Fix IDR memory leak in VDUSE module exit vdpa/mlx5: Fix release of uninitialized resources on error path vhost-scsi: Fix check for inline_sg_cnt exceeding preallocated limit virtio: virtio_dma_buf: fix missing parameter documentation vhost: Fix typos vhost: vringh: Remove unused functions vhost: vringh: Remove unused iotlb functions ...

vhost: basic in order support

2025-08-01T13:11:09+00:00

This patch adds basic in order support for vhost. Two optimizations are implemented in this patch: 1) Since driver uses descriptor in order, vhost can deduce the next avail ring head by counting the number of descriptors that has been used in next_avail_head. This eliminate the need to access the available ring in vhost. 2) vhost_add_used_and_singal_n() is extended to accept the number of batched buffers per used elem. While this increases the times of userspace memory access but it helps to reduce the chance of used ring access of both the driver and vhost. Vhost-net will be the first user for this. Acked-by: Jonah Palmer Signed-off-by: Jason Wang Message-Id: <20250714084755.11921-3-jasowang@redhat.com> Signed-off-by: Michael S. Tsirkin Tested-by: Lei Yang

vhost: Reintroduce kthread API and add mode selection

2025-08-01T13:11:09+00:00

Since commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads"), the vhost uses vhost_task and operates as a child of the owner thread. This is required for correct CPU usage accounting, especially when using containers. However, this change has caused confusion for some legacy userspace applications, and we didn't notice until it's too late. Unfortunately, it's too late to revert - we now have userspace depending both on old and new behaviour :( To address the issue, reintroduce kthread mode for vhost workers and provide a configuration to select between kthread and task worker. - Add 'fork_owner' parameter to vhost_dev to let users select kthread or task mode. Default mode is task mode(VHOST_FORK_OWNER_TASK). - Reintroduce kthread mode support: * Bring back the original vhost_worker() implementation, and renamed to vhost_run_work_kthread_list(). * Add cgroup support for the kthread * Introduce struct vhost_worker_ops: - Encapsulates create / stop / wake‑up callbacks. - vhost_worker_create() selects the proper ops according to inherit_owner. - Userspace configuration interface: * New IOCTLs: - VHOST_SET_FORK_FROM_OWNER lets userspace select task mode (VHOST_FORK_OWNER_TASK) or kthread mode (VHOST_FORK_OWNER_KTHREAD) - VHOST_GET_FORK_FROM_OWNER reads the current worker mode * Expose module parameter 'fork_from_owner_default' to allow system administrators to configure the default mode for vhost workers * Kconfig option CONFIG_VHOST_ENABLE_FORK_OWNER_CONTROL controls whether these IOCTLs and the parameter are available - The VHOST_NEW_WORKER functionality requires fork_owner to be set to true, with validation added to ensure proper configuration This partially reverts or improves upon: commit 6e890c5d5021 ("vhost: use vhost_tasks for worker threads") commit 1cdaafa1b8b4 ("vhost: replace single worker pointer with xarray") Fixes: 6e890c5d5021 ("vhost: use vhost_tasks for worker threads"), Signed-off-by: Cindy Lu Message-Id: <20250714071333.59794-2-lulu@redhat.com> Signed-off-by: Michael S. Tsirkin Acked-by: Jason Wang Tested-by: Lei Yang

vhost-net: allow configuring extended features

2025-07-08T16:05:23+00:00

Use the extended feature type for 'acked_features' and implement two new ioctls operation allowing the user-space to set/query an unbounded amount of features. The actual number of processed features is limited by VIRTIO_FEATURES_MAX and attempts to set features above such limit fail with EOPNOTSUPP. Note that: the legacy ioctls implicitly truncate the negotiated features to the lower 64 bits range and the 'acked_backend_features' field don't need conversion, as the only negotiated feature there is in the low 64 bit range. Acked-by: Jason Wang Signed-off-by: Paolo Abeni

vhost_task: Handle SIGKILL by flushing work and exiting

2024-05-22T12:31:15+00:00

Instead of lingering until the device is closed, this has us handle SIGKILL by: 1. marking the worker as killed so we no longer try to use it with new virtqueues and new flush operations. 2. setting the virtqueue to worker mapping so no new works are queued. 3. running all the exiting works. Suggested-by: Edward Adam Davis Reported-and-tested-by: syzbot+98edc2df894917b3431f@syzkaller.appspotmail.com Message-Id: Signed-off-by: Mike Christie Message-Id: <20240316004707.45557-9-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin

vhost: Remove vhost_vq_flush

2024-05-22T12:31:15+00:00

vhost_vq_flush is no longer used so remove it. Signed-off-by: Mike Christie Message-Id: <20240316004707.45557-5-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin

eventfd: simplify eventfd_signal()

2023-11-28T13:08:38+00:00

Ever since the eventfd type was introduced back in 2007 in commit e1ad7468c77d ("signal/timer/event: eventfd core") the eventfd_signal() function only ever passed 1 as a value for @n. There's no point in keeping that additional argument. Link: https://lore.kernel.org/r/20231122-vfs-eventfd-signal-v2-2-bd549b14ce0c@kernel.org Acked-by: Xu Yilun Acked-by: Andrew Donnellan # ocxl Acked-by: Eric Farman # s390 Reviewed-by: Jan Kara Reviewed-by: Jens Axboe Signed-off-by: Christian Brauner

vhost: Make parameter name match of vhost_get_vq_desc()

2023-07-03T16:15:15+00:00

The parameter name in the function declaration and definition should be the same. drivers/vhost/vhost.h, int vhost_get_vq_desc(..., unsigned int iov_count,...); drivers/vhost/vhost.c, int vhost_get_vq_desc(..., unsigned int iov_size,...) Signed-off-by: Xianting Tian Message-Id: <20230621093835.36878-1-xianting.tian@linux.alibaba.com> Signed-off-by: Michael S. Tsirkin

vhost: Allow worker switching while work is queueing

2023-07-03T16:15:14+00:00

This patch drops the requirement that we can only switch workers if work has not been queued by using RCU for the vq based queueing paths and a mutex for the device wide flush. We can also use this to support SIGKILL properly in the future where we should exit almost immediately after getting that signal. With this patch, when get_signal returns true, we can set the vq->worker to NULL and do a synchronize_rcu to prevent new work from being queued to the vhost_task that has been killed. Signed-off-by: Mike Christie Message-Id: <20230626232307.97930-18-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin