lguest: allow any process to send interrupts

We currently only allow the Launcher process to send interrupts, but it
as we already send interrupts from the hrtimer, it's a simple matter of
extracting that code into a common set_interrupt routine.

As we switch to a thread per virtqueue, this avoids a bottleneck through the
main Launcher process.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/interrupts_and_traps.c

@@ -213,6 +213,20 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
 	if (!more)
 		put_user(0, &cpu->lg->lguest_data->irq_pending);
 }
+
+/* And this is the routine when we want to set an interrupt for the Guest. */
+void set_interrupt(struct lg_cpu *cpu, unsigned int irq)
+{
+	/* Next time the Guest runs, the core code will see if it can deliver
+	 * this interrupt. */
+	set_bit(irq, cpu->irqs_pending);
+
+	/* Make sure it sees it; it might be asleep (eg. halted), or
+	 * running the Guest right now, in which case kick_process()
+	 * will knock it out. */
+	if (!wake_up_process(cpu->tsk))
+		kick_process(cpu->tsk);
+}
 /*:*/
 
 /* Linux uses trap 128 for system calls.  Plan9 uses 64, and Ron Minnich sent
@@ -528,10 +542,7 @@ static enum hrtimer_restart clockdev_fn(struct hrtimer *timer)
 	struct lg_cpu *cpu = container_of(timer, struct lg_cpu, hrt);
 
 	/* Remember the first interrupt is the timer interrupt. */
-	set_bit(0, cpu->irqs_pending);
-	/* Guest may be stopped or running on another CPU. */
-	if (!wake_up_process(cpu->tsk))
-		kick_process(cpu->tsk);
+	set_interrupt(cpu, 0);
 	return HRTIMER_NORESTART;
 }
 

drivers/lguest/lg.h

@@ -143,6 +143,7 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user);
 /* interrupts_and_traps.c: */
 unsigned int interrupt_pending(struct lg_cpu *cpu, bool *more);
 void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more);
+void set_interrupt(struct lg_cpu *cpu, unsigned int irq);
 bool deliver_trap(struct lg_cpu *cpu, unsigned int num);
 void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int i,
 			  u32 low, u32 hi);

drivers/lguest/lguest_user.c

@@ -45,9 +45,8 @@ static int user_send_irq(struct lg_cpu *cpu, const unsigned long __user *input)
 		return -EFAULT;
 	if (irq >= LGUEST_IRQS)
 		return -EINVAL;
-	/* Next time the Guest runs, the core code will see if it can deliver
-	 * this interrupt. */
-	set_bit(irq, cpu->irqs_pending);
+
+	set_interrupt(cpu, irq);
 	return 0;
 }
 
@@ -252,11 +251,6 @@ static ssize_t write(struct file *file, const char __user *in,
 		/* Once the Guest is dead, you can only read() why it died. */
 		if (lg->dead)
 			return -ENOENT;
-
-		/* If you're not the task which owns the Guest, all you can do
-		 * is break the Launcher out of running the Guest. */
-		if (current != cpu->tsk && req != LHREQ_BREAK)
-			return -EPERM;
 	}
 
 	switch (req) {