KVM: x86: Run PIT work in own kthread
We can't run PIT IRQ injection work in the interrupt context of the host
timer. This would allow the user to influence the handler complexity by
asking for a broadcast to a large number of VCPUs. Therefore, this work
was pushed into workqueue context in 9d244caf2e. However, this prevents
prioritizing the PIT injection over other task as workqueues share
kernel threads.
This replaces the workqueue with a kthread worker and gives that thread
a name in the format "kvm-pit/<owner-process-pid>". That allows to
identify and adjust the kthread priority according to the VM process
parameters.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index d68f99d..adba28f 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -34,7 +34,6 @@
#include <linux/kvm_host.h>
#include <linux/slab.h>
-#include <linux/workqueue.h>
#include "irq.h"
#include "i8254.h"
@@ -249,7 +248,7 @@
/* in this case, we had multiple outstanding pit interrupts
* that we needed to inject. Reinject
*/
- queue_work(ps->pit->wq, &ps->pit->expired);
+ queue_kthread_work(&ps->pit->worker, &ps->pit->expired);
ps->irq_ack = 1;
spin_unlock(&ps->inject_lock);
}
@@ -270,7 +269,7 @@
static void destroy_pit_timer(struct kvm_pit *pit)
{
hrtimer_cancel(&pit->pit_state.pit_timer.timer);
- cancel_work_sync(&pit->expired);
+ flush_kthread_work(&pit->expired);
}
static bool kpit_is_periodic(struct kvm_timer *ktimer)
@@ -284,7 +283,7 @@
.is_periodic = kpit_is_periodic,
};
-static void pit_do_work(struct work_struct *work)
+static void pit_do_work(struct kthread_work *work)
{
struct kvm_pit *pit = container_of(work, struct kvm_pit, expired);
struct kvm *kvm = pit->kvm;
@@ -328,7 +327,7 @@
if (ktimer->reinject || !atomic_read(&ktimer->pending)) {
atomic_inc(&ktimer->pending);
- queue_work(pt->wq, &pt->expired);
+ queue_kthread_work(&pt->worker, &pt->expired);
}
if (ktimer->t_ops->is_periodic(ktimer)) {
@@ -353,7 +352,7 @@
/* TODO The new value only affected after the retriggered */
hrtimer_cancel(&pt->timer);
- cancel_work_sync(&ps->pit->expired);
+ flush_kthread_work(&ps->pit->expired);
pt->period = interval;
ps->is_periodic = is_period;
@@ -669,6 +668,8 @@
{
struct kvm_pit *pit;
struct kvm_kpit_state *pit_state;
+ struct pid *pid;
+ pid_t pid_nr;
int ret;
pit = kzalloc(sizeof(struct kvm_pit), GFP_KERNEL);
@@ -685,14 +686,20 @@
mutex_lock(&pit->pit_state.lock);
spin_lock_init(&pit->pit_state.inject_lock);
- pit->wq = create_singlethread_workqueue("kvm-pit-wq");
- if (!pit->wq) {
+ pid = get_pid(task_tgid(current));
+ pid_nr = pid_vnr(pid);
+ put_pid(pid);
+
+ init_kthread_worker(&pit->worker);
+ pit->worker_task = kthread_run(kthread_worker_fn, &pit->worker,
+ "kvm-pit/%d", pid_nr);
+ if (IS_ERR(pit->worker_task)) {
mutex_unlock(&pit->pit_state.lock);
kvm_free_irq_source_id(kvm, pit->irq_source_id);
kfree(pit);
return NULL;
}
- INIT_WORK(&pit->expired, pit_do_work);
+ init_kthread_work(&pit->expired, pit_do_work);
kvm->arch.vpit = pit;
pit->kvm = kvm;
@@ -736,7 +743,7 @@
kvm_unregister_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
kvm_unregister_irq_ack_notifier(kvm, &pit_state->irq_ack_notifier);
kvm_free_irq_source_id(kvm, pit->irq_source_id);
- destroy_workqueue(pit->wq);
+ kthread_stop(pit->worker_task);
kfree(pit);
return NULL;
}
@@ -756,10 +763,10 @@
mutex_lock(&kvm->arch.vpit->pit_state.lock);
timer = &kvm->arch.vpit->pit_state.pit_timer.timer;
hrtimer_cancel(timer);
- cancel_work_sync(&kvm->arch.vpit->expired);
+ flush_kthread_work(&kvm->arch.vpit->expired);
+ kthread_stop(kvm->arch.vpit->worker_task);
kvm_free_irq_source_id(kvm, kvm->arch.vpit->irq_source_id);
mutex_unlock(&kvm->arch.vpit->pit_state.lock);
- destroy_workqueue(kvm->arch.vpit->wq);
kfree(kvm->arch.vpit);
}
}