um: Support dynamic IRQ allocation

It's cumbersome and error-prone to keep adding fixed IRQ numbers,
and for proper device wakeup support for the virtio/vhost-user
support we need to have different IRQs for each device. Even if
in theory two IRQs (with and without wake) might be sufficient,
it's much easier to reason about it when we have dynamic number
assignment. It also makes it easier to add new devices that may
dynamically exist or depending on the configuration, etc.

Add support for this, up to 64 IRQs (the same limit as epoll FDs
we have right now). Since it's not easy to port all the existing
places to dynamic allocation (some data is statically initialized)
keep the low numbers are reserved for the existing hard-coded IRQ
numbers.
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/line.c

@@ -262,19 +262,25 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
 int line_setup_irq(int fd, int input, int output, struct line *line, void *data)
 {
 	const struct line_driver *driver = line->driver;
-	int err = 0;
+	int err;
 
-	if (input)
+	if (input) {
 		err = um_request_irq(driver->read_irq, fd, IRQ_READ,
 				     line_interrupt, IRQF_SHARED,
 				     driver->read_irq_name, data);
-	if (err)
-		return err;
-	if (output)
+		if (err < 0)
+			return err;
+	}
+
+	if (output) {
 		err = um_request_irq(driver->write_irq, fd, IRQ_WRITE,
 				     line_write_interrupt, IRQF_SHARED,
 				     driver->write_irq_name, data);
-	return err;
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
 }
 
 static int line_activate(struct tty_port *port, struct tty_struct *tty)

arch/um/drivers/mconsole_kern.c

@@ -738,7 +738,7 @@ static int __init mconsole_init(void)
 
 	err = um_request_irq(MCONSOLE_IRQ, sock, IRQ_READ, mconsole_interrupt,
 			     IRQF_SHARED, "mconsole", (void *)sock);
-	if (err) {
+	if (err < 0) {
 		printk(KERN_ERR "Failed to get IRQ for management console\n");
 		goto out;
 	}

arch/um/drivers/net_kern.c

@@ -160,7 +160,7 @@ static int uml_net_open(struct net_device *dev)
 
 	err = um_request_irq(dev->irq, lp->fd, IRQ_READ, uml_net_interrupt,
 			     IRQF_SHARED, dev->name, dev);
-	if (err != 0) {
+	if (err < 0) {
 		printk(KERN_ERR "uml_net_open: failed to get irq(%d)\n", err);
 		err = -ENETUNREACH;
 		goto out_close;

arch/um/drivers/port_kern.c

@@ -100,7 +100,7 @@ static int port_accept(struct port_list *port)
 		  .port 	= port });
 
 	if (um_request_irq(TELNETD_IRQ, socket[0], IRQ_READ, pipe_interrupt,
-			  IRQF_SHARED, "telnetd", conn)) {
+			  IRQF_SHARED, "telnetd", conn) < 0) {
 		printk(KERN_ERR "port_accept : failed to get IRQ for "
 		       "telnetd\n");
 		goto out_free;
@@ -182,7 +182,7 @@ void *port_data(int port_num)
 	}
 
 	if (um_request_irq(ACCEPT_IRQ, fd, IRQ_READ, port_interrupt,
-			  IRQF_SHARED, "port", port)) {
+			  IRQF_SHARED, "port", port) < 0) {
 		printk(KERN_ERR "Failed to get IRQ for port %d\n", port_num);
 		goto out_close;
 	}

arch/um/drivers/random.c

@@ -76,7 +76,7 @@ static int __init rng_init (void)
 	random_fd = err;
 	err = um_request_irq(RANDOM_IRQ, random_fd, IRQ_READ, random_interrupt,
 			     0, "random", NULL);
-	if (err)
+	if (err < 0)
 		goto err_out_cleanup_hw;
 
 	sigio_broken(random_fd, 1);

arch/um/drivers/ubd_kern.c

@@ -1253,7 +1253,7 @@ static int __init ubd_driver_init(void){
 	}
 	err = um_request_irq(UBD_IRQ, thread_fd, IRQ_READ, ubd_intr,
 			     0, "ubd", ubd_devs);
-	if(err != 0)
+	if(err < 0)
 		printk(KERN_ERR "um_request_irq failed - errno = %d\n", -err);
 	return 0;
 }

arch/um/drivers/vector_kern.c

@@ -1271,7 +1271,7 @@ static int vector_net_open(struct net_device *dev)
 		irq_rr + VECTOR_BASE_IRQ, vp->fds->rx_fd,
 			IRQ_READ, vector_rx_interrupt,
 			IRQF_SHARED, dev->name, dev);
-	if (err != 0) {
+	if (err < 0) {
 		netdev_err(dev, "vector_open: failed to get rx irq(%d)\n", err);
 		err = -ENETUNREACH;
 		goto out_close;
@@ -1286,7 +1286,7 @@ static int vector_net_open(struct net_device *dev)
 			irq_rr + VECTOR_BASE_IRQ, vp->fds->tx_fd,
 				IRQ_WRITE, vector_tx_interrupt,
 				IRQF_SHARED, dev->name, dev);
-		if (err != 0) {
+		if (err < 0) {
 			netdev_err(dev,
 				"vector_open: failed to get tx irq(%d)\n", err);
 			err = -ENETUNREACH;

arch/um/drivers/virtio_uml.c

@@ -412,7 +412,7 @@ static int vhost_user_init_slave_req(struct virtio_uml_device *vu_dev)
 	rc = um_request_irq(VIRTIO_IRQ, vu_dev->req_fd, IRQ_READ,
 			    vu_req_interrupt, IRQF_SHARED,
 			    vu_dev->pdev->name, vu_dev);
-	if (rc)
+	if (rc < 0)
 		goto err_close;
 
 	rc = vhost_user_send_no_payload_fd(vu_dev, VHOST_USER_SET_SLAVE_REQ_FD,
@@ -854,7 +854,7 @@ static int vu_setup_vq_call_fd(struct virtio_uml_device *vu_dev,
 	info->call_fd = call_fds[0];
 	rc = um_request_irq(VIRTIO_IRQ, info->call_fd, IRQ_READ,
 			    vu_interrupt, IRQF_SHARED, info->name, vq);
-	if (rc)
+	if (rc < 0)
 		goto close_both;
 
 	rc = vhost_user_set_vring_call(vu_dev, vq->index, call_fds[1]);

arch/um/drivers/xterm_kern.c

@@ -51,7 +51,7 @@ int xterm_fd(int socket, int *pid_out)
 
 	err = um_request_irq(XTERM_IRQ, socket, IRQ_READ, xterm_interrupt,
 			     IRQF_SHARED, "xterm", data);
-	if (err) {
+	if (err < 0) {
 		printk(KERN_ERR "xterm_fd : failed to get IRQ for xterm, "
 		       "err = %d\n",  err);
 		ret = err;

arch/um/include/asm/irq.h

@@ -24,14 +24,14 @@
 #define VECTOR_BASE_IRQ		(VIRTIO_IRQ + 1)
 #define VECTOR_IRQ_SPACE	8
 
-#define LAST_IRQ (VECTOR_IRQ_SPACE + VECTOR_BASE_IRQ - 1)
+#define UM_FIRST_DYN_IRQ (VECTOR_IRQ_SPACE + VECTOR_BASE_IRQ)
 
 #else
 
-#define LAST_IRQ VIRTIO_IRQ
+#define UM_FIRST_DYN_IRQ (VIRTIO_IRQ + 1)
 
 #endif
 
-#define NR_IRQS (LAST_IRQ + 1)
+#define NR_IRQS			64
 
 #endif

arch/um/include/shared/irq_kern.h

@@ -9,10 +9,10 @@
 #include <linux/interrupt.h>
 #include <asm/ptrace.h>
 
-extern int um_request_irq(unsigned int irq, int fd, int type,
-			  irq_handler_t handler,
-			  unsigned long irqflags,  const char * devname,
-			  void *dev_id);
-void um_free_irq(unsigned int irq, void *dev);
-#endif
+#define UM_IRQ_ALLOC	-1
 
+int um_request_irq(int irq, int fd, int type, irq_handler_t handler,
+		   unsigned long irqflags,  const char * devname,
+		   void *dev_id);
+void um_free_irq(int irq, void *dev_id);
+#endif

arch/um/kernel/irq.c

@@ -19,6 +19,7 @@
 #include <kern_util.h>
 #include <os.h>
 #include <irq_user.h>
+#include <irq_kern.h>
 
 
 extern void free_irqs(void);
@@ -38,6 +39,7 @@ struct irq_entry {
 static struct irq_entry *active_fds;
 
 static DEFINE_SPINLOCK(irq_lock);
+static DECLARE_BITMAP(irqs_allocated, NR_IRQS);
 
 static void irq_io_loop(struct irq_fd *irq, struct uml_pt_regs *regs)
 {
@@ -421,27 +423,52 @@ unsigned int do_IRQ(int irq, struct uml_pt_regs *regs)
 	return 1;
 }
 
-void um_free_irq(unsigned int irq, void *dev)
+void um_free_irq(int irq, void *dev)
 {
+	if (WARN(irq < 0 || irq > NR_IRQS, "freeing invalid irq %d", irq))
+		return;
+
 	free_irq_by_irq_and_dev(irq, dev);
 	free_irq(irq, dev);
+	clear_bit(irq, irqs_allocated);
 }
 EXPORT_SYMBOL(um_free_irq);
 
-int um_request_irq(unsigned int irq, int fd, int type,
+int um_request_irq(int irq, int fd, int type,
 		   irq_handler_t handler,
 		   unsigned long irqflags, const char * devname,
 		   void *dev_id)
 {
 	int err;
 
+	if (irq == UM_IRQ_ALLOC) {
+		int i;
+
+		for (i = UM_FIRST_DYN_IRQ; i < NR_IRQS; i++) {
+			if (!test_and_set_bit(i, irqs_allocated)) {
+				irq = i;
+				break;
+			}
+		}
+	}
+
+	if (irq < 0)
+		return -ENOSPC;
+
 	if (fd != -1) {
 		err = activate_fd(irq, fd, type, dev_id);
 		if (err)
-			return err;
+			goto error;
 	}
 
-	return request_irq(irq, handler, irqflags, devname, dev_id);
+	err = request_irq(irq, handler, irqflags, devname, dev_id);
+	if (err < 0)
+		goto error;
+
+	return irq;
+error:
+	clear_bit(irq, irqs_allocated);
+	return err;
 }
 
 EXPORT_SYMBOL(um_request_irq);
@@ -480,7 +507,7 @@ void __init init_IRQ(void)
 	irq_set_chip_and_handler(TIMER_IRQ, &SIGVTALRM_irq_type, handle_edge_irq);
 
 
-	for (i = 1; i <= LAST_IRQ; i++)
+	for (i = 1; i < NR_IRQS; i++)
 		irq_set_chip_and_handler(i, &normal_irq_type, handle_edge_irq);
 	/* Initialize EPOLL Loop */
 	os_setup_epoll();

arch/um/kernel/sigio.c

@@ -25,7 +25,7 @@ int write_sigio_irq(int fd)
 
 	err = um_request_irq(SIGIO_WRITE_IRQ, fd, IRQ_READ, sigio_interrupt,
 			     0, "write sigio", NULL);
-	if (err) {
+	if (err < 0) {
 		printk(KERN_ERR "write_sigio_irq : um_request_irq failed, "
 		       "err = %d\n", err);
 		return -1;