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Commit 6082f2e2 authored by Junaid Shahid's avatar Junaid Shahid Committed by Greg Kroah-Hartman
Browse files

kvm: Add helper function for creating VM worker threads 



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: default avatarJunaid Shahid <junaids@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 5219505f

include/linux/kvm_host.h

+6 −0
Original line number Diff line number Diff line
@@ -1305,4 +1305,10 @@ static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu) 
}

#endif /* CONFIG_HAVE_KVM_VCPU_RUN_PID_CHANGE */



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

virt/kvm/kvm_main.c

+84 −0
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ 
#include <linux/slab.h>

#include <linux/sort.h>

#include <linux/bsearch.h>

#include <linux/kthread.h>



#include <asm/processor.h>

#include <asm/io.h>
@@ -4142,3 +4143,86 @@ 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;

}