From e297cd54b3f81d652456ae6cb93941fc6b5c6683 Mon Sep 17 00:00:00 2001 From: Mike Christie Date: Fri, 10 Mar 2023 16:03:30 -0600 Subject: vhost_task: Allow vhost layer to use copy_process Qemu will create vhost devices in the kernel which perform network, SCSI, etc IO and management operations from worker threads created by the kthread API. Because the kthread API does a copy_process on the kthreadd thread, the vhost layer has to use kthread_use_mm to access the Qemu thread's memory and cgroup_attach_task_all to add itself to the Qemu thread's cgroups, and it bypasses the RLIMIT_NPROC limit which can result in VMs creating more threads than the admin expected. This patch adds a new struct vhost_task which can be used instead of kthreads. They allow the vhost layer to use copy_process and inherit the userspace process's mm and cgroups, the task is accounted for under the userspace's nproc count and can be seen in its process tree, and other features like namespaces work and are inherited by default. Signed-off-by: Mike Christie Acked-by: Michael S. Tsirkin Signed-off-by: Christian Brauner (Microsoft) Signed-off-by: Christian Brauner --- MAINTAINERS | 2 ++ 1 file changed, 2 insertions(+) (limited to 'MAINTAINERS') diff --git a/MAINTAINERS b/MAINTAINERS index 8d5bc223f305..186d37c2b4e0 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -22176,7 +22176,9 @@ L: virtualization@lists.linux-foundation.org L: netdev@vger.kernel.org S: Maintained T: git git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git +F: kernel/vhost_task.c F: drivers/vhost/ +F: include/linux/sched/vhost_task.h F: include/linux/vhost_iotlb.h F: include/uapi/linux/vhost.h -- cgit v1.2.3-73-gaa49b