kernel/linux.git/include/uapi/linux/vhost.h, branch v6.12.80

vhost: Fix ioctl # for VHOST_[GS]ET_FORK_FROM_OWNER

2025-09-04T13:31:43+00:00

[ Upstream commit 24fc631539cc78225f5c61f99c7666fcff48024d ] The VHOST_[GS]ET_FEATURES_ARRAY ioctl already took 0x83 and it would result in a build error when the vhost uapi header is used for perf tool build like below. In file included from trace/beauty/ioctl.c:93: tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c: In function ‘ioctl__scnprintf_vhost_virtio_cmd’: tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c:36:18: error: initialized field overwritten [-Werror=override-init] 36 | [0x83] = "SET_FORK_FROM_OWNER", | ^~~~~~~~~~~~~~~~~~~~~ tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c:36:18: note: (near initialization for ‘vhost_virtio_ioctl_cmds[131]’) Fixes: 7d9896e9f6d02d8a ("vhost: Reintroduce kthread API and add mode selection") Signed-off-by: Namhyung Kim Message-Id: <20250819063958.833770-1-namhyung@kernel.org> Signed-off-by: Michael S. Tsirkin Tested-by: Lei Yang Signed-off-by: Sasha Levin

vhost: Reintroduce kthread API and add mode selection

2025-08-15T10:13:58+00:00

[ Upstream commit 7d9896e9f6d02d8aa85e63f736871f96c59a5263 ] 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 Signed-off-by: Sasha Levin

vhost-vdpa: change ioctl # for VDPA_GET_VRING_SIZE

2024-04-08T08:11:04+00:00

VDPA_GET_VRING_SIZE by mistake uses the already occupied ioctl # 0x80 and we never noticed - it happens to work because the direction and size are different, but confuses tools such as perf which like to look at just the number, and breaks the extra robustness of the ioctl numbering macros. To fix, sort the entries and renumber the ioctl - not too late since it wasn't in any released kernels yet. Cc: Arnaldo Carvalho de Melo Reported-by: Namhyung Kim Fixes: 1496c47065f9 ("vhost-vdpa: uapi to support reporting per vq size") Cc: "Zhu Lingshan" Signed-off-by: Michael S. Tsirkin Message-Id: <41c1c5489688abe5bfef9f7cf15584e3fb872ac5.1712092759.git.mst@redhat.com> Reviewed-by: Eugenio Pérez Reviewed-by: Zhu Lingshan Reviewed-by: Stefano Garzarella Acked-by: Jason Wang

vhost-vdpa: uapi to support reporting per vq size

2024-03-19T06:45:49+00:00

The size of a virtqueue is a per vq configuration. This commit introduce a new ioctl uAPI to support this flexibility. Signed-off-by: Zhu Lingshan Message-Id: <20240202163905.8834-2-lingshan.zhu@intel.com> Signed-off-by: Michael S. Tsirkin

vhost-vdpa: uAPI to get dedicated descriptor group id

2023-11-01T13:19:55+00:00

With _F_DESC_ASID backend feature, the device can now support the VHOST_VDPA_GET_VRING_DESC_GROUP ioctl, and it may expose the descriptor table (including avail and used ring) in a different group than the buffers it contains. This new uAPI will fetch the group ID of the descriptor table. Signed-off-by: Si-Wei Liu Acked-by: Eugenio Pérez Acked-by: Jason Wang Message-Id: <20231018171456.1624030-6-dtatulea@nvidia.com> Signed-off-by: Michael S. Tsirkin Reviewed-by: Si-Wei Liu Tested-by: Si-Wei Liu Tested-by: Lei Yang

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

vhost: allow userspace to create workers

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

For vhost-scsi with 3 vqs or more and a workload that tries to use them in parallel like: fio --filename=/dev/sdb --direct=1 --rw=randrw --bs=4k \ --ioengine=libaio --iodepth=128 --numjobs=3 the single vhost worker thread will become a bottlneck and we are stuck at around 500K IOPs no matter how many jobs, virtqueues, and CPUs are used. To better utilize virtqueues and available CPUs, this patch allows userspace to create workers and bind them to vqs. You can have N workers per dev and also share N workers with M vqs on that dev. This patch adds the interface related code and the next patch will hook vhost-scsi into it. The patches do not try to hook net and vsock into the interface because: 1. multiple workers don't seem to help vsock. The problem is that with only 2 virtqueues we never fully use the existing worker when doing bidirectional tests. This seems to match vhost-scsi where we don't see the worker as a bottleneck until 3 virtqueues are used. 2. net already has a way to use multiple workers. Signed-off-by: Mike Christie Message-Id: <20230626232307.97930-16-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin

vhost-vdpa: uAPI to resume the device

2023-02-21T00:26:56+00:00

This new ioctl adds support for resuming the device from userspace. This is required when trying to restore the device in a functioning state after it's been suspended. It is already possible to reset a suspended device, but that means the device must be reconfigured and all the IOMMU/IOTLB mappings must be recreated. This new operation allows the device to be resumed without going through a full reset. This is particularly useful when trying to perform offline migration of a virtual machine (also known as snapshot/restore) as it allows the VMM to resume the virtual machine back to a running state after the snapshot is performed. Acked-by: Jason Wang Signed-off-by: Sebastien Boeuf Message-Id: <73b75fb87d25cff59768b4955a81fe7ffe5b4770.1672742878.git.sebastien.boeuf@intel.com> Signed-off-by: Michael S. Tsirkin Reviewed-by: Stefano Garzarella

vhost-vdpa: uAPI to suspend the device

2022-08-11T08:31:15+00:00

The ioctl adds support for suspending the device from userspace. This is a must before getting virtqueue indexes (base) for live migration, since the device could modify them after userland gets them. There are individual ways to perform that action for some devices (VHOST_NET_SET_BACKEND, VHOST_VSOCK_SET_RUNNING, ...) but there was no way to perform it for any vhost device (and, in particular, vhost-vdpa). After a successful return of the ioctl call the device must not process more virtqueue descriptors. The device can answer to read or writes of config fields as if it were not suspended. In particular, writing to "queue_enable" with a value of 1 will not make the device start processing buffers of the virtqueue. Signed-off-by: Eugenio Pérez Message-Id: <20220810171512.2343333-4-eperezma@redhat.com> Signed-off-by: Michael S. Tsirkin

vhost-vdpa: introduce uAPI to set group ASID

2022-05-31T16:44:31+00:00

Follows the vDPA support for associating ASID to a specific virtqueue group. This patch adds a uAPI to support setting them from userspace. Signed-off-by: Jason Wang Signed-off-by: Gautam Dawar Message-Id: <20220330180436.24644-15-gdawar@xilinx.com> Signed-off-by: Michael S. Tsirkin