kernel/linux.git/drivers/vhost/vhost.c, branch v6.12.80

vhost: Fix kthread worker cgroup failure handling

2025-12-18T12:55:10+00:00

[ Upstream commit f3f64c2eaffbc3169bbe1e5d1e897e6dacc839d1 ] If we fail to attach to a cgroup we are leaking the id. This adds a new goto to free the id. Fixes: 7d9896e9f6d0 ("vhost: Reintroduce kthread API and add mode selection") Signed-off-by: Mike Christie Acked-by: Jason Wang Reviewed-by: Chaitanya Kulkarni Signed-off-by: Michael S. Tsirkin Message-Id: <20251101194358.13605-1-michael.christie@oracle.com> Signed-off-by: Sasha Levin

vhost: fail early when __vhost_add_used() fails

2025-08-20T16:30:40+00:00

[ Upstream commit b4ba1207d45adaafa2982c035898b36af2d3e518 ] This patch fails vhost_add_used_n() early when __vhost_add_used() fails to make sure used idx is not updated with stale used ring information. Reported-by: Eugenio Pérez Signed-off-by: Jason Wang Message-Id: <20250714084755.11921-2-jasowang@redhat.com> 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: return task creation error instead of NULL

2025-03-22T19:54:21+00:00

[ Upstream commit cb380909ae3b1ebf14d6a455a4f92d7916d790cb ] Lets callers distinguish why the vhost task creation failed. No one currently cares why it failed, so no real runtime change from this patch, but that will not be the case for long. Signed-off-by: Keith Busch Message-ID: <20250227230631.303431-2-kbusch@meta.com> Reviewed-by: Mike Christie Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin

vhost: move smp_rmb() into vhost_get_avail_idx()

2024-07-09T12:42:40+00:00

All callers of vhost_get_avail_idx() use smp_rmb() to order the available ring entry read and avail_idx read. Make vhost_get_avail_idx() call smp_rmb() itself whenever the avail_idx is accessed. This way, the callers don't need to worry about the memory barrier. As a side benefit, we also validate the index on all paths now, which will hopefully help prevent/catch earlier future bugs. Note that current code is inconsistent in how the errors are handled. They are treated as an empty ring in some places, but as non-empty ring in other places. This patch doesn't attempt to change the existing behaviour. No functional change intended. Signed-off-by: Michael S. Tsirkin Reviewed-by: Gavin Shan Acked-by: Will Deacon Message-Id: <20240429232748.642356-1-gshan@redhat.com>

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: Release worker mutex during flushes

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

In the next patches where the worker can be killed while in use, we need to be able to take the worker mutex and kill queued works for new IO and flushes, and set some new flags to prevent new __vhost_vq_attach_worker calls from swapping in/out killed workers. If we are holding the worker mutex during a flush and the flush's work is still in the queue, the worker code that will handle the SIGKILL cleanup won't be able to take the mutex and perform it's cleanup. So this patch has us drop the worker mutex while waiting for the flush to complete. Signed-off-by: Mike Christie Message-Id: <20240316004707.45557-8-michael.christie@oracle.com> Signed-off-by: Michael S. Tsirkin

vhost: Use virtqueue mutex for swapping worker

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

__vhost_vq_attach_worker uses the vhost_dev mutex to serialize the swapping of a virtqueue's worker. This was done for simplicity because we are already holding that mutex. In the next patches where the worker can be killed while in use, we need finer grained locking because some drivers will hold the vhost_dev mutex while flushing. However in the SIGKILL handler in the next patches, we will need to be able to swap workers (set current one to NULL), kill queued works and stop new flushes while flushes are in progress. To prepare us, this has us use the virtqueue mutex for swapping workers instead of the vhost_dev one. Signed-off-by: Mike Christie Message-Id: <20240316004707.45557-7-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

vhost: correct misleading printing information

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

Guest moved avail idx not used idx when we need to print log if '(vq->avail_idx - last_avail_idx) > vq->num', so fix it. Signed-off-by: Xianting Tian Message-Id: <20240311082109.46773-1-xianting.tian@linux.alibaba.com> Signed-off-by: Michael S. Tsirkin