From: Junaid Shahid junaids@google.com
commit c57c80467f90e5504c8df9ad3555d2c78800bf94 upstream.
Add a function to create a kernel thread associated with a given VM. In particular, it ensures that the worker thread inherits the priority and cgroups of the calling thread.
Signed-off-by: Junaid Shahid junaids@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Thomas Gleixner tglx@linutronix.de [bwh: Backported to 4.9: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/kvm_host.h | 6 +++ virt/kvm/kvm_main.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 90 insertions(+)
--- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1208,4 +1208,10 @@ static inline bool vcpu_valid_wakeup(str } #endif /* CONFIG_HAVE_KVM_INVALID_WAKEUPS */
+typedef int (*kvm_vm_thread_fn_t)(struct kvm *kvm, uintptr_t data); + +int kvm_vm_create_worker_thread(struct kvm *kvm, kvm_vm_thread_fn_t thread_fn, + uintptr_t data, const char *name, + struct task_struct **thread_ptr); + #endif --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -49,6 +49,7 @@ #include <linux/slab.h> #include <linux/sort.h> #include <linux/bsearch.h> +#include <linux/kthread.h>
#include <asm/processor.h> #include <asm/io.h> @@ -3987,3 +3988,86 @@ void kvm_exit(void) kvm_vfio_ops_exit(); } EXPORT_SYMBOL_GPL(kvm_exit); + +struct kvm_vm_worker_thread_context { + struct kvm *kvm; + struct task_struct *parent; + struct completion init_done; + kvm_vm_thread_fn_t thread_fn; + uintptr_t data; + int err; +}; + +static int kvm_vm_worker_thread(void *context) +{ + /* + * The init_context is allocated on the stack of the parent thread, so + * we have to locally copy anything that is needed beyond initialization + */ + struct kvm_vm_worker_thread_context *init_context = context; + struct kvm *kvm = init_context->kvm; + kvm_vm_thread_fn_t thread_fn = init_context->thread_fn; + uintptr_t data = init_context->data; + int err; + + err = kthread_park(current); + /* kthread_park(current) is never supposed to return an error */ + WARN_ON(err != 0); + if (err) + goto init_complete; + + err = cgroup_attach_task_all(init_context->parent, current); + if (err) { + kvm_err("%s: cgroup_attach_task_all failed with err %d\n", + __func__, err); + goto init_complete; + } + + set_user_nice(current, task_nice(init_context->parent)); + +init_complete: + init_context->err = err; + complete(&init_context->init_done); + init_context = NULL; + + if (err) + return err; + + /* Wait to be woken up by the spawner before proceeding. */ + kthread_parkme(); + + if (!kthread_should_stop()) + err = thread_fn(kvm, data); + + return err; +} + +int kvm_vm_create_worker_thread(struct kvm *kvm, kvm_vm_thread_fn_t thread_fn, + uintptr_t data, const char *name, + struct task_struct **thread_ptr) +{ + struct kvm_vm_worker_thread_context init_context = {}; + struct task_struct *thread; + + *thread_ptr = NULL; + init_context.kvm = kvm; + init_context.parent = current; + init_context.thread_fn = thread_fn; + init_context.data = data; + init_completion(&init_context.init_done); + + thread = kthread_run(kvm_vm_worker_thread, &init_context, + "%s-%d", name, task_pid_nr(current)); + if (IS_ERR(thread)) + return PTR_ERR(thread); + + /* kthread_run is never supposed to return NULL */ + WARN_ON(thread == NULL); + + wait_for_completion(&init_context.init_done); + + if (!init_context.err) + *thread_ptr = thread; + + return init_context.err; +}