lguest: remove obsolete LHREQ_BREAK call

We no longer need an efficient mechanism to force the Guest back into
host userspace, as each device is serviced without bothering the main
Guest process (aka. the Launcher).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/core.c

@@ -209,10 +209,6 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
 		if (signal_pending(current))
 			return -ERESTARTSYS;
 
-		/* If Waker set break_out, return to Launcher. */
-		if (cpu->break_out)
-			return -EAGAIN;
-
 		/* Check if there are any interrupts which can be delivered now:
 		 * if so, this sets up the hander to be executed when we next
 		 * run the Guest. */
@@ -231,13 +227,12 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
 			break;
 
 		/* If the Guest asked to be stopped, we sleep.  The Guest's
-		 * clock timer or LHREQ_BREAK from the Waker will wake us. */
+		 * clock timer will wake us. */
 		if (cpu->halted) {
 			set_current_state(TASK_INTERRUPTIBLE);
-			/* Just before we sleep, make sure nothing snuck in
+			/* Just before we sleep, make sure no interrupt snuck in
 			 * which we should be doing. */
-			if (interrupt_pending(cpu, &more) < LGUEST_IRQS
-			    || cpu->break_out)
+			if (interrupt_pending(cpu, &more) < LGUEST_IRQS)
 				set_current_state(TASK_RUNNING);
 			else
 				schedule();

drivers/lguest/lg.h

@@ -71,9 +71,7 @@ struct lg_cpu {
 	/* Virtual clock device */
 	struct hrtimer hrt;
 
-	/* Do we need to stop what we're doing and return to userspace? */
-	int break_out;
-	wait_queue_head_t break_wq;
+	/* Did the Guest tell us to halt? */
 	int halted;
 
 	/* Pending virtual interrupts */

drivers/lguest/lguest_user.c

@@ -11,32 +11,6 @@
 #include <linux/file.h>
 #include "lg.h"
 
-/*L:055 When something happens, the Waker process needs a way to stop the
- * kernel running the Guest and return to the Launcher.  So the Waker writes
- * LHREQ_BREAK and the value "1" to /dev/lguest to do this.  Once the Launcher
- * has done whatever needs attention, it writes LHREQ_BREAK and "0" to release
- * the Waker. */
-static int break_guest_out(struct lg_cpu *cpu, const unsigned long __user*input)
-{
-	unsigned long on;
-
-	/* Fetch whether they're turning break on or off. */
-	if (get_user(on, input) != 0)
-		return -EFAULT;
-
-	if (on) {
-		cpu->break_out = 1;
-		if (!wake_up_process(cpu->tsk))
-			kick_process(cpu->tsk);
-		/* Wait for them to reset it */
-		return wait_event_interruptible(cpu->break_wq, !cpu->break_out);
-	} else {
-		cpu->break_out = 0;
-		wake_up(&cpu->break_wq);
-		return 0;
-	}
-}
-
 bool send_notify_to_eventfd(struct lg_cpu *cpu)
 {
 	unsigned int i;
@@ -202,9 +176,6 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip)
 	 * address. */
 	lguest_arch_setup_regs(cpu, start_ip);
 
-	/* Initialize the queue for the Waker to wait on */
-	init_waitqueue_head(&cpu->break_wq);
-
 	/* We keep a pointer to the Launcher task (ie. current task) for when
 	 * other Guests want to wake this one (eg. console input). */
 	cpu->tsk = current;
@@ -344,8 +315,6 @@ static ssize_t write(struct file *file, const char __user *in,
 		return initialize(file, input);
 	case LHREQ_IRQ:
 		return user_send_irq(cpu, input);
-	case LHREQ_BREAK:
-		return break_guest_out(cpu, input);
 	case LHREQ_EVENTFD:
 		return attach_eventfd(lg, input);
 	default:

include/linux/lguest_launcher.h

@@ -57,7 +57,7 @@ enum lguest_req
 	LHREQ_INITIALIZE, /* + base, pfnlimit, start */
 	LHREQ_GETDMA, /* No longer used */
 	LHREQ_IRQ, /* + irq */
-	LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
+	LHREQ_BREAK, /* No longer used */
 	LHREQ_EVENTFD, /* + address, fd. */
 };