1 files changed, 259 insertions, 574 deletions

diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 02fa524cf4ad..5470b8ed2149 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -16,6 +16,7 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/wait.h>
+#include <sys/eventfd.h>
 #include <fcntl.h>
 #include <stdbool.h>
 #include <errno.h>
@@ -59,7 +60,6 @@ typedef uint8_t u8;
 /*:*/
 
 #define PAGE_PRESENT 0x7        /* Present, RW, Execute */
-#define NET_PEERNUM 1
 #define BRIDGE_PFX "bridge:"
 #ifndef SIOCBRADDIF
 #define SIOCBRADDIF     0x89a2          /* add interface to bridge      */
@@ -76,18 +76,10 @@ static bool verbose;
         do { if (verbose) printf(args); } while(0)
 /*:*/
 
-/* File descriptors for the Waker. */
-struct {
-        int pipe[2];
-} waker_fds;
-
 /* The pointer to the start of guest memory. */
 static void *guest_base;
 /* The maximum guest physical address allowed, and maximum possible. */
 static unsigned long guest_limit, guest_max;
-/* The pipe for signal hander to write to. */
-static int timeoutpipe[2];
-static unsigned int timeout_usec = 500;
 /* The /dev/lguest file descriptor. */
 static int lguest_fd;
 
@@ -97,11 +89,6 @@ static unsigned int __thread cpu_id;
 /* This is our list of devices. */
 struct device_list
 {
-        /* Summary information about the devices in our list: ready to pass to
-         * select() to ask which need servicing.*/
-        fd_set infds;
-        int max_infd;
-
         /* Counter to assign interrupt numbers. */
         unsigned int next_irq;
 
@@ -137,16 +124,11 @@ struct device
         /* The name of this device, for --verbose. */
         const char *name;
 
-        /* If handle_input is set, it wants to be called when this file
-         * descriptor is ready. */
-        int fd;
-        bool (*handle_input)(struct device *me);
-
         /* Any queues attached to this device */
         struct virtqueue *vq;
 
-        /* Handle status being finalized (ie. feature bits stable). */
-        void (*ready)(struct device *me);
+        /* Is it operational */
+        bool running;
 
         /* Device-specific data. */
         void *priv;
@@ -169,16 +151,20 @@ struct virtqueue
         /* Last available index we saw. */
         u16 last_avail_idx;
 
-        /* The routine to call when the Guest pings us, or timeout. */
-        void (*handle_output)(struct virtqueue *me, bool timeout);
+        /* Eventfd where Guest notifications arrive. */
+        int eventfd;
 
-        /* Is this blocked awaiting a timer? */
-        bool blocked;
+        /* Function for the thread which is servicing this virtqueue. */
+        void (*service)(struct virtqueue *vq);
+        pid_t thread;
 };
 
 /* Remember the arguments to the program so we can "reboot" */
 static char **main_args;
 
+/* The original tty settings to restore on exit. */
+static struct termios orig_term;
+
 /* We have to be careful with barriers: our devices are all run in separate
  * threads and so we need to make sure that changes visible to the Guest happen
  * in precise order. */
@@ -521,78 +507,6 @@ static void tell_kernel(unsigned long start)
 }
 /*:*/
 
-static void add_device_fd(int fd)
-{
-        FD_SET(fd, &devices.infds);
-        if (fd > devices.max_infd)
-                devices.max_infd = fd;
-}
-
-/*L:200
- * The Waker.
- *
- * With console, block and network devices, we can have lots of input which we
- * need to process.  We could try to tell the kernel what file descriptors to
- * watch, but handing a file descriptor mask through to the kernel is fairly
- * icky.
- *
- * Instead, we clone off a thread which watches the file descriptors and writes
- * the LHREQ_BREAK command to the /dev/lguest file descriptor to tell the Host
- * stop running the Guest.  This causes the Launcher to return from the
- * /dev/lguest read with -EAGAIN, where it will write to /dev/lguest to reset
- * the LHREQ_BREAK and wake us up again.
- *
- * This, of course, is merely a different *kind* of icky.
- *
- * Given my well-known antipathy to threads, I'd prefer to use processes.  But
- * it's easier to share Guest memory with threads, and trivial to share the
- * devices.infds as the Launcher changes it.
- */
-static int waker(void *unused)
-{
-        /* Close the write end of the pipe: only the Launcher has it open. */
-        close(waker_fds.pipe[1]);
-
-        for (;;) {
-                fd_set rfds = devices.infds;
-                unsigned long args[] = { LHREQ_BREAK, 1 };
-                unsigned int maxfd = devices.max_infd;
-
-                /* We also listen to the pipe from the Launcher. */
-                FD_SET(waker_fds.pipe[0], &rfds);
-                if (waker_fds.pipe[0] > maxfd)
-                        maxfd = waker_fds.pipe[0];
-
-                /* Wait until input is ready from one of the devices. */
-                select(maxfd+1, &rfds, NULL, NULL, NULL);
-
-                /* Message from Launcher? */
-                if (FD_ISSET(waker_fds.pipe[0], &rfds)) {
-                        char c;
-                        /* If this fails, then assume Launcher has exited.
-                         * Don't do anything on exit: we're just a thread! */
-                        if (read(waker_fds.pipe[0], &c, 1) != 1)
-                                _exit(0);
-                        continue;
-                }
-
-                /* Send LHREQ_BREAK command to snap the Launcher out of it. */
-                pwrite(lguest_fd, args, sizeof(args), cpu_id);
-        }
-        return 0;
-}
-
-/* This routine just sets up a pipe to the Waker process. */
-static void setup_waker(void)
-{
-        /* This pipe is closed when Launcher dies, telling Waker. */
-        if (pipe(waker_fds.pipe) != 0)
-                err(1, "Creating pipe for Waker");
-
-        if (clone(waker, malloc(4096) + 4096, CLONE_VM | SIGCHLD, NULL) == -1)
-                err(1, "Creating Waker");
-}
-
 /*
  * Device Handling.
  *
@@ -642,25 +556,27 @@ static unsigned next_desc(struct virtqueue *vq, unsigned int i)
  * number of output then some number of input descriptors, it's actually two
  * iovecs, but we pack them into one and note how many of each there were.
  *
- * This function returns the descriptor number found, or vq->vring.num (which
- * is never a valid descriptor number) if none was found. */
-static unsigned get_vq_desc(struct virtqueue *vq,
-                            struct iovec iov[],
-                            unsigned int *out_num, unsigned int *in_num)
+ * This function returns the descriptor number found. */
+static unsigned wait_for_vq_desc(struct virtqueue *vq,
+                                 struct iovec iov[],
+                                 unsigned int *out_num, unsigned int *in_num)
 {
         unsigned int i, head;
-        u16 last_avail;
+        u16 last_avail = lg_last_avail(vq);
+
+        while (last_avail == vq->vring.avail->idx) {
+                u64 event;
+
+                /* Nothing new?  Wait for eventfd to tell us they refilled. */
+                if (read(vq->eventfd, &event, sizeof(event)) != sizeof(event))
+                        errx(1, "Event read failed?");
+        }
 
         /* Check it isn't doing very strange things with descriptor numbers. */
-        last_avail = lg_last_avail(vq);
         if ((u16)(vq->vring.avail->idx - last_avail) > vq->vring.num)
                 errx(1, "Guest moved used index from %u to %u",
                      last_avail, vq->vring.avail->idx);
 
-        /* If there's nothing new since last we looked, return invalid. */
-        if (vq->vring.avail->idx == last_avail)
-                return vq->vring.num;
-
         /* Grab the next descriptor number they're advertising, and increment
          * the index we've seen. */
         head = vq->vring.avail->ring[last_avail % vq->vring.num];
@@ -740,15 +656,7 @@ static void add_used_and_trigger(struct virtqueue *vq, unsigned head, int len)
 /*
  * The Console
  *
- * Here is the input terminal setting we save, and the routine to restore them
- * on exit so the user gets their terminal back. */
-static struct termios orig_term;
-static void restore_term(void)
-{
-        tcsetattr(STDIN_FILENO, TCSANOW, &orig_term);
-}
-
-/* We associate some data with the console for our exit hack. */
+ * We associate some data with the console for our exit hack. */
 struct console_abort
 {
         /* How many times have they hit ^C? */
@@ -758,245 +666,235 @@ struct console_abort
 };
 
 /* This is the routine which handles console input (ie. stdin). */
-static bool handle_console_input(struct device *dev)
+static void console_input(struct virtqueue *vq)
 {
         int len;
         unsigned int head, in_num, out_num;
-        struct iovec iov[dev->vq->vring.num];
-        struct console_abort *abort = dev->priv;
-
-        /* First we need a console buffer from the Guests's input virtqueue. */
-        head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
-
-        /* If they're not ready for input, stop listening to this file
-         * descriptor.  We'll start again once they add an input buffer. */
-        if (head == dev->vq->vring.num)
-                return false;
+        struct console_abort *abort = vq->dev->priv;
+        struct iovec iov[vq->vring.num];
 
+        /* Make sure there's a descriptor waiting. */
+        head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
         if (out_num)
                 errx(1, "Output buffers in console in queue?");
 
-        /* This is why we convert to iovecs: the readv() call uses them, and so
-         * it reads straight into the Guest's buffer. */
-        len = readv(dev->fd, iov, in_num);
+        /* Read it in. */
+        len = readv(STDIN_FILENO, iov, in_num);
         if (len <= 0) {
-                /* This implies that the console is closed, is /dev/null, or
-                 * something went terribly wrong. */
+                /* Ran out of input? */
                 warnx("Failed to get console input, ignoring console.");
-                /* Put the input terminal back. */
-                restore_term();
-                /* Remove callback from input vq, so it doesn't restart us. */
-                dev->vq->handle_output = NULL;
-                /* Stop listening to this fd: don't call us again. */
-                return false;
+                /* For simplicity, dying threads kill the whole Launcher.  So
+                 * just nap here. */
+                for (;;)
+                        pause();
         }
 
-        /* Tell the Guest about the new input. */
-        add_used_and_trigger(dev->vq, head, len);
+        add_used_and_trigger(vq, head, len);
 
         /* Three ^C within one second?  Exit.
          *
-         * This is such a hack, but works surprisingly well.  Each ^C has to be
-         * in a buffer by itself, so they can't be too fast.  But we check that
-         * we get three within about a second, so they can't be too slow. */
-        if (len == 1 && ((char *)iov[0].iov_base)[0] == 3) {
-                if (!abort->count++)
-                        gettimeofday(&abort->start, NULL);
-                else if (abort->count == 3) {
-                        struct timeval now;
-                        gettimeofday(&now, NULL);
-                        if (now.tv_sec <= abort->start.tv_sec+1) {
-                                unsigned long args[] = { LHREQ_BREAK, 0 };
-                                /* Close the fd so Waker will know it has to
-                                 * exit. */
-                                close(waker_fds.pipe[1]);
-                                /* Just in case Waker is blocked in BREAK, send
-                                 * unbreak now. */
-                                write(lguest_fd, args, sizeof(args));
-                                exit(2);
-                        }
-                        abort->count = 0;
-                }
-        } else
-                /* Any other key resets the abort counter. */
+         * This is such a hack, but works surprisingly well.  Each ^C has to
+         * be in a buffer by itself, so they can't be too fast.  But we check
+         * that we get three within about a second, so they can't be too
+         * slow. */
+        if (len != 1 || ((char *)iov[0].iov_base)[0] != 3) {
                 abort->count = 0;
+                return;
+        }
 
-        /* Everything went OK! */
-        return true;
+        abort->count++;
+        if (abort->count == 1)
+                gettimeofday(&abort->start, NULL);
+        else if (abort->count == 3) {
+                struct timeval now;
+                gettimeofday(&now, NULL);
+                /* Kill all Launcher processes with SIGINT, like normal ^C */
+                if (now.tv_sec <= abort->start.tv_sec+1)
+                        kill(0, SIGINT);
+                abort->count = 0;
+        }
 }
 
-/* Handling output for console is simple: we just get all the output buffers
- * and write them to stdout. */
-static void handle_console_output(struct virtqueue *vq, bool timeout)
+/* This is the routine which handles console output (ie. stdout). */
+static void console_output(struct virtqueue *vq)
 {
         unsigned int head, out, in;
         struct iovec iov[vq->vring.num];
 
-        /* Keep getting output buffers from the Guest until we run out. */
-        while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
-                if (in)
-                        errx(1, "Input buffers in output queue?");
-                while (!iov_empty(iov, out)) {
-                        int len = writev(STDOUT_FILENO, iov, out);
-                        if (len <= 0)
-                                err(1, "Write to stdout gave %i", len);
-                        iov_consume(iov, out, len);
-                }
-                add_used_and_trigger(vq, head, 0);
+        head = wait_for_vq_desc(vq, iov, &out, &in);
+        if (in)
+                errx(1, "Input buffers in console output queue?");
+        while (!iov_empty(iov, out)) {
+                int len = writev(STDOUT_FILENO, iov, out);
+                if (len <= 0)
+                        err(1, "Write to stdout gave %i", len);
+                iov_consume(iov, out, len);
         }
-}
-
-/* This is called when we no longer want to hear about Guest changes to a
- * virtqueue.  This is more efficient in high-traffic cases, but it means we
- * have to set a timer to check if any more changes have occurred. */
-static void block_vq(struct virtqueue *vq)
-{
-        struct itimerval itm;
-
-        vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
-        vq->blocked = true;
-
-        itm.it_interval.tv_sec = 0;
-        itm.it_interval.tv_usec = 0;
-        itm.it_value.tv_sec = 0;
-        itm.it_value.tv_usec = timeout_usec;
-
-        setitimer(ITIMER_REAL, &itm, NULL);
+        add_used_and_trigger(vq, head, 0);
 }
 
 /*
  * The Network
  *
  * Handling output for network is also simple: we get all the output buffers
- * and write them (ignoring the first element) to this device's file descriptor
- * (/dev/net/tun).
+ * and write them to /dev/net/tun.
  */
-static void handle_net_output(struct virtqueue *vq, bool timeout)
+struct net_info {
+        int tunfd;
+};
+
+static void net_output(struct virtqueue *vq)
 {
-        unsigned int head, out, in, num = 0;
+        struct net_info *net_info = vq->dev->priv;
+        unsigned int head, out, in;
         struct iovec iov[vq->vring.num];
-        static int last_timeout_num;
-
-        /* Keep getting output buffers from the Guest until we run out. */
-        while ((head = get_vq_desc(vq, iov, &out, &in)) != vq->vring.num) {
-                if (in)
-                        errx(1, "Input buffers in output queue?");
-                if (writev(vq->dev->fd, iov, out) < 0)
-                        err(1, "Writing network packet to tun");
-                add_used_and_trigger(vq, head, 0);
-                num++;
-        }
 
-        /* Block further kicks and set up a timer if we saw anything. */
-        if (!timeout && num)
-                block_vq(vq);
-
-        /* We never quite know how long should we wait before we check the
-         * queue again for more packets.  We start at 500 microseconds, and if
-         * we get fewer packets than last time, we assume we made the timeout
-         * too small and increase it by 10 microseconds.  Otherwise, we drop it
-         * by one microsecond every time.  It seems to work well enough. */
-        if (timeout) {
-                if (num < last_timeout_num)
-                        timeout_usec += 10;
-                else if (timeout_usec > 1)
-                        timeout_usec--;
-                last_timeout_num = num;
-        }
+        head = wait_for_vq_desc(vq, iov, &out, &in);
+        if (in)
+                errx(1, "Input buffers in net output queue?");
+        if (writev(net_info->tunfd, iov, out) < 0)
+                errx(1, "Write to tun failed?");
+        add_used_and_trigger(vq, head, 0);
 }
 
-/* This is where we handle a packet coming in from the tun device to our
+/* This is where we handle packets coming in from the tun device to our
  * Guest. */
-static bool handle_tun_input(struct device *dev)
+static void net_input(struct virtqueue *vq)
 {
-        unsigned int head, in_num, out_num;
         int len;
-        struct iovec iov[dev->vq->vring.num];
-
-        /* First we need a network buffer from the Guests's recv virtqueue. */
-        head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
-        if (head == dev->vq->vring.num) {
-                /* Now, it's expected that if we try to send a packet too
-                 * early, the Guest won't be ready yet.  Wait until the device
-                 * status says it's ready. */
-                /* FIXME: Actually want DRIVER_ACTIVE here. */
-
-                /* Now tell it we want to know if new things appear. */
-                dev->vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
-                wmb();
-
-                /* We'll turn this back on if input buffers are registered. */
-                return false;
-        } else if (out_num)
-                errx(1, "Output buffers in network recv queue?");
-
-        /* Read the packet from the device directly into the Guest's buffer. */
-        len = readv(dev->fd, iov, in_num);
+        unsigned int head, out, in;
+        struct iovec iov[vq->vring.num];
+        struct net_info *net_info = vq->dev->priv;
+
+        head = wait_for_vq_desc(vq, iov, &out, &in);
+        if (out)
+                errx(1, "Output buffers in net input queue?");
+        len = readv(net_info->tunfd, iov, in);
         if (len <= 0)
-                err(1, "reading network");
+                err(1, "Failed to read from tun.");
+        add_used_and_trigger(vq, head, len);
+}
 
-        /* Tell the Guest about the new packet. */
-        add_used_and_trigger(dev->vq, head, len);
+/* This is the helper to create threads. */
+static int do_thread(void *_vq)
+{
+        struct virtqueue *vq = _vq;
 
-        verbose("tun input packet len %i [%02x %02x] (%s)\n", len,
-                ((u8 *)iov[1].iov_base)[0], ((u8 *)iov[1].iov_base)[1],
-                head != dev->vq->vring.num ? "sent" : "discarded");
+        for (;;)
+                vq->service(vq);
+        return 0;
+}
 
-        /* All good. */
-        return true;
+/* When a child dies, we kill our entire process group with SIGTERM.  This
+ * also has the side effect that the shell restores the console for us! */
+static void kill_launcher(int signal)
+{
+        kill(0, SIGTERM);
 }
 
-/*L:215 This is the callback attached to the network and console input
- * virtqueues: it ensures we try again, in case we stopped console or net
- * delivery because Guest didn't have any buffers. */
-static void enable_fd(struct virtqueue *vq, bool timeout)
+static void reset_device(struct device *dev)
 {
-        add_device_fd(vq->dev->fd);
-        /* Snap the Waker out of its select loop. */
-        write(waker_fds.pipe[1], "", 1);
+        struct virtqueue *vq;
+
+        verbose("Resetting device %s\n", dev->name);
+
+        /* Clear any features they've acked. */
+        memset(get_feature_bits(dev) + dev->feature_len, 0, dev->feature_len);
+
+        /* We're going to be explicitly killing threads, so ignore them. */
+        signal(SIGCHLD, SIG_IGN);
+
+        /* Zero out the virtqueues, get rid of their threads */
+        for (vq = dev->vq; vq; vq = vq->next) {
+                if (vq->thread != (pid_t)-1) {
+                        kill(vq->thread, SIGTERM);
+                        waitpid(vq->thread, NULL, 0);
+                        vq->thread = (pid_t)-1;
+                }
+                memset(vq->vring.desc, 0,
+                       vring_size(vq->config.num, LGUEST_VRING_ALIGN));
+                lg_last_avail(vq) = 0;
+        }
+        dev->running = false;
+
+        /* Now we care if threads die. */
+        signal(SIGCHLD, (void *)kill_launcher);
 }
 
-static void net_enable_fd(struct virtqueue *vq, bool timeout)
+static void create_thread(struct virtqueue *vq)
 {
-        /* We don't need to know again when Guest refills receive buffer. */
-        vq->vring.used->flags |= VRING_USED_F_NO_NOTIFY;
-        enable_fd(vq, timeout);
+        /* Create stack for thread and run it.  Since stack grows
+         * upwards, we point the stack pointer to the end of this
+         * region. */
+        char *stack = malloc(32768);
+        unsigned long args[] = { LHREQ_EVENTFD,
+                                 vq->config.pfn*getpagesize(), 0 };
+
+        /* Create a zero-initialized eventfd. */
+        vq->eventfd = eventfd(0, 0);
+        if (vq->eventfd < 0)
+                err(1, "Creating eventfd");
+        args[2] = vq->eventfd;
+
+        /* Attach an eventfd to this virtqueue: it will go off
+         * when the Guest does an LHCALL_NOTIFY for this vq. */
+        if (write(lguest_fd, &args, sizeof(args)) != 0)
+                err(1, "Attaching eventfd");
+
+        /* CLONE_VM: because it has to access the Guest memory, and
+         * SIGCHLD so we get a signal if it dies. */
+        vq->thread = clone(do_thread, stack + 32768, CLONE_VM | SIGCHLD, vq);
+        if (vq->thread == (pid_t)-1)
+                err(1, "Creating clone");
+        /* We close our local copy, now the child has it. */
+        close(vq->eventfd);
 }
 
-/* When the Guest tells us they updated the status field, we handle it. */
-static void update_device_status(struct device *dev)
+static void start_device(struct device *dev)
 {
+        unsigned int i;
         struct virtqueue *vq;
 
-        /* This is a reset. */
-        if (dev->desc->status == 0) {
-                verbose("Resetting device %s\n", dev->name);
+        verbose("Device %s OK: offered", dev->name);
+        for (i = 0; i < dev->feature_len; i++)
+                verbose(" %02x", get_feature_bits(dev)[i]);
+        verbose(", accepted");
+        for (i = 0; i < dev->feature_len; i++)
+                verbose(" %02x", get_feature_bits(dev)
+                        [dev->feature_len+i]);
+
+        for (vq = dev->vq; vq; vq = vq->next) {
+                if (vq->service)
+                        create_thread(vq);
+        }
+        dev->running = true;
+}
+
+static void cleanup_devices(void)
+{
+        struct device *dev;
+
+        for (dev = devices.dev; dev; dev = dev->next)
+                reset_device(dev);
 
-                /* Clear any features they've acked. */
-                memset(get_feature_bits(dev) + dev->feature_len, 0,
-                       dev->feature_len);
+        /* If we saved off the original terminal settings, restore them now. */
+        if (orig_term.c_lflag & (ISIG|ICANON|ECHO))
+                tcsetattr(STDIN_FILENO, TCSANOW, &orig_term);
+}
 
-                /* Zero out the virtqueues. */
-                for (vq = dev->vq; vq; vq = vq->next) {
-                        memset(vq->vring.desc, 0,
-                               vring_size(vq->config.num, LGUEST_VRING_ALIGN));
-                        lg_last_avail(vq) = 0;
-                }
-        } else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) {
+/* When the Guest tells us they updated the status field, we handle it. */
+static void update_device_status(struct device *dev)
+{
+        /* A zero status is a reset, otherwise it's a set of flags. */
+        if (dev->desc->status == 0)
+                reset_device(dev);
+        else if (dev->desc->status & VIRTIO_CONFIG_S_FAILED) {
                 warnx("Device %s configuration FAILED", dev->name);
+                if (dev->running)
+                        reset_device(dev);
         } else if (dev->desc->status & VIRTIO_CONFIG_S_DRIVER_OK) {
-                unsigned int i;
-
-                verbose("Device %s OK: offered", dev->name);
-                for (i = 0; i < dev->feature_len; i++)
-                        verbose(" %02x", get_feature_bits(dev)[i]);
-                verbose(", accepted");
-                for (i = 0; i < dev->feature_len; i++)
-                        verbose(" %02x", get_feature_bits(dev)
-                                [dev->feature_len+i]);
-
-                if (dev->ready)
-                        dev->ready(dev);
+                if (!dev->running)
+                        start_device(dev);
         }
 }
 
@@ -1004,32 +902,24 @@ static void update_device_status(struct device *dev)
 static void handle_output(unsigned long addr)
 {
         struct device *i;
-        struct virtqueue *vq;
 
-        /* Check each device and virtqueue. */
+        /* Check each device. */
         for (i = devices.dev; i; i = i->next) {
+                struct virtqueue *vq;
+
                 /* Notifications to device descriptors update device status. */
                 if (from_guest_phys(addr) == i->desc) {
                         update_device_status(i);
                         return;
                 }
 
-                /* Notifications to virtqueues mean output has occurred. */
+                /* Devices *can* be used before status is set to DRIVER_OK. */
                 for (vq = i->vq; vq; vq = vq->next) {
-                        if (vq->config.pfn != addr/getpagesize())
+                        if (addr != vq->config.pfn*getpagesize())
                                 continue;
-
-                        /* Guest should acknowledge (and set features!)  before
-                         * using the device. */
-                        if (i->desc->status == 0) {
-                                warnx("%s gave early output", i->name);
-                                return;
-                        }
-
-                        if (strcmp(vq->dev->name, "console") != 0)
-                                verbose("Output to %s\n", vq->dev->name);
-                        if (vq->handle_output)
-                                vq->handle_output(vq, false);
+                        if (i->running)
+                                errx(1, "Notification on running %s", i->name);
+                        start_device(i);
                         return;
                 }
         }
@@ -1043,71 +933,6 @@ static void handle_output(unsigned long addr)
               strnlen(from_guest_phys(addr), guest_limit - addr));
 }
 
-static void handle_timeout(void)
-{
-        char buf[32];
-        struct device *i;
-        struct virtqueue *vq;
-
-        /* Clear the pipe */
-        read(timeoutpipe[0], buf, sizeof(buf));
-
-        /* Check each device and virtqueue: flush blocked ones. */
-        for (i = devices.dev; i; i = i->next) {
-                for (vq = i->vq; vq; vq = vq->next) {
-                        if (!vq->blocked)
-                                continue;
-
-                        vq->vring.used->flags &= ~VRING_USED_F_NO_NOTIFY;
-                        vq->blocked = false;
-                        if (vq->handle_output)
-                                vq->handle_output(vq, true);
-                }
-        }
-}
-
-/* This is called when the Waker wakes us up: check for incoming file
- * descriptors. */
-static void handle_input(void)
-{
-        /* select() wants a zeroed timeval to mean "don't wait". */
-        struct timeval poll = { .tv_sec = 0, .tv_usec = 0 };
-
-        for (;;) {
-                struct device *i;
-                fd_set fds = devices.infds;
-                int num;
-
-                num = select(devices.max_infd+1, &fds, NULL, NULL, &poll);
-                /* Could get interrupted */
-                if (num < 0)
-                        continue;
-                /* If nothing is ready, we're done. */
-                if (num == 0)
-                        break;
-
-                /* Otherwise, call the device(s) which have readable file
-                 * descriptors and a method of handling them.  */
-                for (i = devices.dev; i; i = i->next) {
-                        if (i->handle_input && FD_ISSET(i->fd, &fds)) {
-                                if (i->handle_input(i))
-                                        continue;
-
-                                /* If handle_input() returns false, it means we
-                                 * should no longer service it.  Networking and
-                                 * console do this when there's no input
-                                 * buffers to deliver into.  Console also uses
-                                 * it when it discovers that stdin is closed. */
-                                FD_CLR(i->fd, &devices.infds);
-                        }
-                }
-
-                /* Is this the timeout fd? */
-                if (FD_ISSET(timeoutpipe[0], &fds))
-                        handle_timeout();
-        }
-}
-
 /*L:190
  * Device Setup
  *
@@ -1153,7 +978,7 @@ static struct lguest_device_desc *new_dev_desc(u16 type)
 /* Each device descriptor is followed by the description of its virtqueues.  We
  * specify how many descriptors the virtqueue is to have. */
 static void add_virtqueue(struct device *dev, unsigned int num_descs,
-                          void (*handle_output)(struct virtqueue *, bool))
+                          void (*service)(struct virtqueue *))
 {
         unsigned int pages;
         struct virtqueue **i, *vq = malloc(sizeof(*vq));
@@ -1168,7 +993,8 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
         vq->next = NULL;
         vq->last_avail_idx = 0;
         vq->dev = dev;
-        vq->blocked = false;
+        vq->service = service;
+        vq->thread = (pid_t)-1;
 
         /* Initialize the configuration. */
         vq->config.num = num_descs;
@@ -1193,15 +1019,6 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
          * second.  */
         for (i = &dev->vq; *i; i = &(*i)->next);
         *i = vq;
-
-        /* Set the routine to call when the Guest does something to this
-         * virtqueue. */
-        vq->handle_output = handle_output;
-
-        /* As an optimization, set the advisory "Don't Notify Me" flag if we
-         * don't have a handler */
-        if (!handle_output)
-                vq->vring.used->flags = VRING_USED_F_NO_NOTIFY;
 }
 
 /* The first half of the feature bitmask is for us to advertise features.  The
@@ -1237,24 +1054,17 @@ static void set_config(struct device *dev, unsigned len, const void *conf)
  * calling new_dev_desc() to allocate the descriptor and device memory.
  *
  * See what I mean about userspace being boring? */
-static struct device *new_device(const char *name, u16 type, int fd,
-                                 bool (*handle_input)(struct device *))
+static struct device *new_device(const char *name, u16 type)
 {
         struct device *dev = malloc(sizeof(*dev));
 
         /* Now we populate the fields one at a time. */
-        dev->fd = fd;
-        /* If we have an input handler for this file descriptor, then we add it
-         * to the device_list's fdset and maxfd. */
-        if (handle_input)
-                add_device_fd(dev->fd);
         dev->desc = new_dev_desc(type);
-        dev->handle_input = handle_input;
         dev->name = name;
         dev->vq = NULL;
-        dev->ready = NULL;
         dev->feature_len = 0;
         dev->num_vq = 0;
+        dev->running = false;
 
         /* Append to device list.  Prepending to a single-linked list is
          * easier, but the user expects the devices to be arranged on the bus
@@ -1282,13 +1092,10 @@ static void setup_console(void)
                  * raw input stream to the Guest. */
                 term.c_lflag &= ~(ISIG|ICANON|ECHO);
                 tcsetattr(STDIN_FILENO, TCSANOW, &term);
-                /* If we exit gracefully, the original settings will be
-                 * restored so the user can see what they're typing. */
-                atexit(restore_term);
         }
 
-        dev = new_device("console", VIRTIO_ID_CONSOLE,
-                         STDIN_FILENO, handle_console_input);
+        dev = new_device("console", VIRTIO_ID_CONSOLE);
+
         /* We store the console state in dev->priv, and initialize it. */
         dev->priv = malloc(sizeof(struct console_abort));
         ((struct console_abort *)dev->priv)->count = 0;
@@ -1297,31 +1104,13 @@ static void setup_console(void)
          * they put something the input queue, we make sure we're listening to
          * stdin.  When they put something in the output queue, we write it to
          * stdout. */
-        add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd);
-        add_virtqueue(dev, VIRTQUEUE_NUM, handle_console_output);
+        add_virtqueue(dev, VIRTQUEUE_NUM, console_input);
+        add_virtqueue(dev, VIRTQUEUE_NUM, console_output);
 
-        verbose("device %u: console\n", devices.device_num++);
+        verbose("device %u: console\n", ++devices.device_num);
 }
 /*:*/
 
-static void timeout_alarm(int sig)
-{
-        write(timeoutpipe[1], "", 1);
-}
-
-static void setup_timeout(void)
-{
-        if (pipe(timeoutpipe) != 0)
-                err(1, "Creating timeout pipe");
-
-        if (fcntl(timeoutpipe[1], F_SETFL,
-                  fcntl(timeoutpipe[1], F_GETFL) | O_NONBLOCK) != 0)
-                err(1, "Making timeout pipe nonblocking");
-
-        add_device_fd(timeoutpipe[0]);
-        signal(SIGALRM, timeout_alarm);
-}
-
 /*M:010 Inter-guest networking is an interesting area.  Simplest is to have a
  * --sharenet=<name> option which opens or creates a named pipe.  This can be
  * used to send packets to another guest in a 1:1 manner.
@@ -1443,21 +1232,23 @@ static int get_tun_device(char tapif[IFNAMSIZ])
 static void setup_tun_net(char *arg)
 {
         struct device *dev;
-        int netfd, ipfd;
+        struct net_info *net_info = malloc(sizeof(*net_info));
+        int ipfd;
         u32 ip = INADDR_ANY;
         bool bridging = false;
         char tapif[IFNAMSIZ], *p;
         struct virtio_net_config conf;
 
-        netfd = get_tun_device(tapif);
+        net_info->tunfd = get_tun_device(tapif);
 
         /* First we create a new network device. */
-        dev = new_device("net", VIRTIO_ID_NET, netfd, handle_tun_input);
+        dev = new_device("net", VIRTIO_ID_NET);
+        dev->priv = net_info;
 
         /* Network devices need a receive and a send queue, just like
          * console. */
-        add_virtqueue(dev, VIRTQUEUE_NUM, net_enable_fd);
-        add_virtqueue(dev, VIRTQUEUE_NUM, handle_net_output);
+        add_virtqueue(dev, VIRTQUEUE_NUM, net_input);
+        add_virtqueue(dev, VIRTQUEUE_NUM, net_output);
 
         /* We need a socket to perform the magic network ioctls to bring up the
          * tap interface, connect to the bridge etc.  Any socket will do! */
@@ -1546,20 +1337,18 @@ struct vblk_info
  * Remember that the block device is handled by a separate I/O thread.  We head
  * straight into the core of that thread here:
  */
-static bool service_io(struct device *dev)
+static void blk_request(struct virtqueue *vq)
 {
-        struct vblk_info *vblk = dev->priv;
+        struct vblk_info *vblk = vq->dev->priv;
         unsigned int head, out_num, in_num, wlen;
         int ret;
         u8 *in;
         struct virtio_blk_outhdr *out;
-        struct iovec iov[dev->vq->vring.num];
+        struct iovec iov[vq->vring.num];
         off64_t off;
 
-        /* See if there's a request waiting.  If not, nothing to do. */
-        head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
-        if (head == dev->vq->vring.num)
-                return false;
+        /* Get the next request. */
+        head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
 
         /* Every block request should contain at least one output buffer
          * (detailing the location on disk and the type of request) and one
@@ -1633,83 +1422,21 @@ static bool service_io(struct device *dev)
         if (out->type & VIRTIO_BLK_T_BARRIER)
                 fdatasync(vblk->fd);
 
-        /* We can't trigger an IRQ, because we're not the Launcher.  It does
-         * that when we tell it we're done. */
-        add_used(dev->vq, head, wlen);
-        return true;
-}
-
-/* This is the thread which actually services the I/O. */
-static int io_thread(void *_dev)
-{
-        struct device *dev = _dev;
-        struct vblk_info *vblk = dev->priv;
-        char c;
-
-        /* Close other side of workpipe so we get 0 read when main dies. */
-        close(vblk->workpipe[1]);
-        /* Close the other side of the done_fd pipe. */
-        close(dev->fd);
-
-        /* When this read fails, it means Launcher died, so we follow. */
-        while (read(vblk->workpipe[0], &c, 1) == 1) {
-                /* We acknowledge each request immediately to reduce latency,
-                 * rather than waiting until we've done them all.  I haven't
-                 * measured to see if it makes any difference.
-                 *
-                 * That would be an interesting test, wouldn't it?  You could
-                 * also try having more than one I/O thread. */
-                while (service_io(dev))
-                        write(vblk->done_fd, &c, 1);
-        }
-        return 0;
-}
-
-/* Now we've seen the I/O thread, we return to the Launcher to see what happens
- * when that thread tells us it's completed some I/O. */
-static bool handle_io_finish(struct device *dev)
-{
-        char c;
-
-        /* If the I/O thread died, presumably it printed the error, so we
-         * simply exit. */
-        if (read(dev->fd, &c, 1) != 1)
-                exit(1);
-
-        /* It did some work, so trigger the irq. */
-        trigger_irq(dev->vq);
-        return true;
-}
-
-/* When the Guest submits some I/O, we just need to wake the I/O thread. */
-static void handle_virtblk_output(struct virtqueue *vq, bool timeout)
-{
-        struct vblk_info *vblk = vq->dev->priv;
-        char c = 0;
-
-        /* Wake up I/O thread and tell it to go to work! */
-        if (write(vblk->workpipe[1], &c, 1) != 1)
-                /* Presumably it indicated why it died. */
-                exit(1);
+        add_used_and_trigger(vq, head, wlen);
 }
 
 /*L:198 This actually sets up a virtual block device. */
 static void setup_block_file(const char *filename)
 {
-        int p[2];
         struct device *dev;
         struct vblk_info *vblk;
-        void *stack;
         struct virtio_blk_config conf;
 
-        /* This is the pipe the I/O thread will use to tell us I/O is done. */
-        pipe(p);
-
         /* The device responds to return from I/O thread. */
-        dev = new_device("block", VIRTIO_ID_BLOCK, p[0], handle_io_finish);
+        dev = new_device("block", VIRTIO_ID_BLOCK);
 
         /* The device has one virtqueue, where the Guest places requests. */
-        add_virtqueue(dev, VIRTQUEUE_NUM, handle_virtblk_output);
+        add_virtqueue(dev, VIRTQUEUE_NUM, blk_request);
 
         /* Allocate the room for our own bookkeeping */
         vblk = dev->priv = malloc(sizeof(*vblk));
@@ -1731,49 +1458,29 @@ static void setup_block_file(const char *filename)
 
         set_config(dev, sizeof(conf), &conf);
 
-        /* The I/O thread writes to this end of the pipe when done. */
-        vblk->done_fd = p[1];
-
-        /* This is the second pipe, which is how we tell the I/O thread about
-         * more work. */
-        pipe(vblk->workpipe);
-
-        /* Create stack for thread and run it.  Since stack grows upwards, we
-         * point the stack pointer to the end of this region. */
-        stack = malloc(32768);
-        /* SIGCHLD - We dont "wait" for our cloned thread, so prevent it from
-         * becoming a zombie. */
-        if (clone(io_thread, stack + 32768, CLONE_VM | SIGCHLD, dev) == -1)
-                err(1, "Creating clone");
-
-        /* We don't need to keep the I/O thread's end of the pipes open. */
-        close(vblk->done_fd);
-        close(vblk->workpipe[0]);
-
         verbose("device %u: virtblock %llu sectors\n",
-                devices.device_num, le64_to_cpu(conf.capacity));
+                ++devices.device_num, le64_to_cpu(conf.capacity));
 }
 
+struct rng_info {
+        int rfd;
+};
+
 /* Our random number generator device reads from /dev/random into the Guest's
  * input buffers.  The usual case is that the Guest doesn't want random numbers
  * and so has no buffers although /dev/random is still readable, whereas
  * console is the reverse.
  *
  * The same logic applies, however. */
-static bool handle_rng_input(struct device *dev)
+static void rng_input(struct virtqueue *vq)
 {
         int len;
         unsigned int head, in_num, out_num, totlen = 0;
-        struct iovec iov[dev->vq->vring.num];
+        struct rng_info *rng_info = vq->dev->priv;
+        struct iovec iov[vq->vring.num];
 
         /* First we need a buffer from the Guests's virtqueue. */
-        head = get_vq_desc(dev->vq, iov, &out_num, &in_num);
-
-        /* If they're not ready for input, stop listening to this file
-         * descriptor.  We'll start again once they add an input buffer. */
-        if (head == dev->vq->vring.num)
-                return false;
-
+        head = wait_for_vq_desc(vq, iov, &out_num, &in_num);
         if (out_num)
                 errx(1, "Output buffers in rng?");
 
@@ -1781,7 +1488,7 @@ static bool handle_rng_input(struct device *dev)
          * it reads straight into the Guest's buffer.  We loop to make sure we
          * fill it. */
         while (!iov_empty(iov, in_num)) {
-                len = readv(dev->fd, iov, in_num);
+                len = readv(rng_info->rfd, iov, in_num);
                 if (len <= 0)
                         err(1, "Read from /dev/random gave %i", len);
                 iov_consume(iov, in_num, len);
@@ -1789,25 +1496,23 @@ static bool handle_rng_input(struct device *dev)
         }
 
         /* Tell the Guest about the new input. */
-        add_used_and_trigger(dev->vq, head, totlen);
-
-        /* Everything went OK! */
-        return true;
+        add_used_and_trigger(vq, head, totlen);
 }
 
 /* And this creates a "hardware" random number device for the Guest. */
 static void setup_rng(void)
 {
         struct device *dev;
-        int fd;
+        struct rng_info *rng_info = malloc(sizeof(*rng_info));
 
-        fd = open_or_die("/dev/random", O_RDONLY);
+        rng_info->rfd = open_or_die("/dev/random", O_RDONLY);
 
         /* The device responds to return from I/O thread. */
-        dev = new_device("rng", VIRTIO_ID_RNG, fd, handle_rng_input);
+        dev = new_device("rng", VIRTIO_ID_RNG);
+        dev->priv = rng_info;
 
         /* The device has one virtqueue, where the Guest places inbufs. */
-        add_virtqueue(dev, VIRTQUEUE_NUM, enable_fd);
+        add_virtqueue(dev, VIRTQUEUE_NUM, rng_input);
 
         verbose("device %u: rng\n", devices.device_num++);
 }
@@ -1823,7 +1528,9 @@ static void __attribute__((noreturn)) restart_guest(void)
         for (i = 3; i < FD_SETSIZE; i++)
                 close(i);
 
-        /* The exec automatically gets rid of the I/O and Waker threads. */
+        /* Reset all the devices (kills all threads). */
+        cleanup_devices();
+
         execv(main_args[0], main_args);
         err(1, "Could not exec %s", main_args[0]);
 }
@@ -1833,7 +1540,6 @@ static void __attribute__((noreturn)) restart_guest(void)
 static void __attribute__((noreturn)) run_guest(void)
 {
         for (;;) {
-                unsigned long args[] = { LHREQ_BREAK, 0 };
                 unsigned long notify_addr;
                 int readval;
 
@@ -1845,7 +1551,6 @@ static void __attribute__((noreturn)) run_guest(void)
                 if (readval == sizeof(notify_addr)) {
                         verbose("Notify on address %#lx\n", notify_addr);
                         handle_output(notify_addr);
-                        continue;
                 /* ENOENT means the Guest died.  Reading tells us why. */
                 } else if (errno == ENOENT) {
                         char reason[1024] = { 0 };
@@ -1854,19 +1559,9 @@ static void __attribute__((noreturn)) run_guest(void)
                 /* ERESTART means that we need to reboot the guest */
                 } else if (errno == ERESTART) {
                         restart_guest();
-                /* EAGAIN means a signal (timeout).
-                 * Anything else means a bug or incompatible change. */
-                } else if (errno != EAGAIN)
+                /* Anything else means a bug or incompatible change. */
+                } else
                         err(1, "Running guest failed");
-
-                /* Only service input on thread for CPU 0. */
-                if (cpu_id != 0)
-                        continue;
-
-                /* Service input, then unset the BREAK to release the Waker. */
-                handle_input();
-                if (pwrite(lguest_fd, args, sizeof(args), cpu_id) < 0)
-                        err(1, "Resetting break");
         }
 }
 /*L:240
@@ -1909,18 +1604,10 @@ int main(int argc, char *argv[])
 
         /* Save the args: we "reboot" by execing ourselves again. */
         main_args = argv;
-        /* We don't "wait" for the children, so prevent them from becoming
-         * zombies. */
-        signal(SIGCHLD, SIG_IGN);
 
-        /* First we initialize the device list.  Since console and network
-         * device receive input from a file descriptor, we keep an fdset
-         * (infds) and the maximum fd number (max_infd) with the head of the
-         * list.  We also keep a pointer to the last device.  Finally, we keep
-         * the next interrupt number to use for devices (1: remember that 0 is
-         * used by the timer). */
-        FD_ZERO(&devices.infds);
-        devices.max_infd = -1;
+        /* First we initialize the device list.  We keep a pointer to the last
+         * device, and the next interrupt number to use for devices (1:
+         * remember that 0 is used by the timer). */
         devices.lastdev = NULL;
         devices.next_irq = 1;
 
@@ -1978,9 +1665,6 @@ int main(int argc, char *argv[])
         /* We always have a console device */
         setup_console();
 
-        /* We can timeout waiting for Guest network transmit. */
-        setup_timeout();
-
         /* Now we load the kernel */
         start = load_kernel(open_or_die(argv[optind+1], O_RDONLY));
 
@@ -2021,10 +1705,11 @@ int main(int argc, char *argv[])
          * /dev/lguest file descriptor. */
         tell_kernel(start);
 
-        /* We clone off a thread, which wakes the Launcher whenever one of the
-         * input file descriptors needs attention.  We call this the Waker, and
-         * we'll cover it in a moment. */
-        setup_waker();
+        /* Ensure that we terminate if a child dies. */
+        signal(SIGCHLD, kill_launcher);
+
+        /* If we exit via err(), this kills all the threads, restores tty. */
+        atexit(cleanup_devices);
 
         /* Finally, run the Guest.  This doesn't return. */
         run_guest();