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kvm: Add helper function for creating VM worker threads 

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>
This commit is contained in:
Junaid Shahid 2019-11-04 12:22:02 +01:00 committed by Thomas Gleixner
parent b8e8c8303f
commit c57c80467f
2 changed files with 90 additions and 0 deletions
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6
include/linux/kvm_host.h
View File

@ -1382,4 +1382,10 @@ 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

84
virt/kvm/kvm_main.c
View File

@ -50,6 +50,7 @@
#include <linux/bsearch.h>
#include <linux/io.h>
#include <linux/lockdep.h>
#include <linux/kthread.h>
#include <asm/processor.h>
#include <asm/ioctl.h>
@ -4371,3 +4372,86 @@ 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;
}