[Xen-devel] [PATCH] VirtioConsole support.

[Miche Baker-Harvey <miche@xxxxxxxxxx>]

Multiple HVC console terminals enabled.

Serialize device and port open and initialization.  Added a mutex
which gates the handling of control messages in virtio_console.c.
This includes adding and removing ports, and making opened ports be
consoles.  Extended the use of the prvdata spinlock to cover some missed
modifications to prvdata.next_vtermno.

I also added a mutex in hvc_console::hvc_alloc() to coordinate waiting
for the driver to be ready, and for the one-time call to hvc_init().  It
had been the case that this was sometimes being called mulitple times, and
partially setup state was being used by the second caller of hvc_alloc().

Make separate struct console* for each new port.  There was a single static
struct console* hvc_console, to be used for early printk.  We aren't doing
early printk, but more importantly, there is no code to multiplex on that
one console.  Multiple virtio_console ports were "sharing" this, which was
disasterous since both the index and the flags for the console are stored
there. The console struct is remembered in the hvc_struct, and it is
deallocated when the hvc_struct is deallocated.

------------------

Konrad, thanks for trying this out on Xen.
This is working in my KVM environment, letting me start multiple
virtio_consoles with getty's on them, but I'm really not sure how
all the console pieces fit together yet.  Feedback is welcome.

Signed-off-by: Miche Baker-Harvey <miche@xxxxxxxxxx>
---
 drivers/char/virtio_console.c |   22 +++++++++++++++++++---
 drivers/tty/hvc/hvc_console.c |   39 +++++++++++++++++++++++++++++++++------
 drivers/tty/hvc/hvc_console.h |    1 +
 3 files changed, 53 insertions(+), 9 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index fb68b12..e819d46 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -24,6 +24,7 @@
 #include <linux/fs.h>
 #include <linux/init.h>
 #include <linux/list.h>
+#include <linux/mutex.h>
 #include <linux/poll.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
@@ -95,6 +96,11 @@ struct console {
        u32 vtermno;
 };
 
+/* serialize the handling of control messages, which includes
+ * the initialization of the virtio_consoles.
+ */
+static DEFINE_MUTEX(virtio_console_mutex);
+
 struct port_buffer {
        char *buf;
 
@@ -979,8 +985,14 @@ int init_port_console(struct port *port)
         * pointers.  The final argument is the output buffer size: we
         * can do any size, so we put PAGE_SIZE here.
         */
-       port->cons.vtermno = pdrvdata.next_vtermno;
+       spin_lock_irq(&pdrvdata_lock);
+       port->cons.vtermno = pdrvdata.next_vtermno++;
+       spin_unlock_irq(&pdrvdata_lock);
 
+       /*
+        * xxx Use index 0 for now assuming there is no early HVC, since
+        * we don't support it.
+        */
        port->cons.hvc = hvc_alloc(port->cons.vtermno, 0, &hv_ops, PAGE_SIZE);
        if (IS_ERR(port->cons.hvc)) {
                ret = PTR_ERR(port->cons.hvc);
@@ -990,7 +1002,6 @@ int init_port_console(struct port *port)
                return ret;
        }
        spin_lock_irq(&pdrvdata_lock);
-       pdrvdata.next_vtermno++;
        list_add_tail(&port->cons.list, &pdrvdata.consoles);
        spin_unlock_irq(&pdrvdata_lock);
        port->guest_connected = true;
@@ -1317,7 +1328,6 @@ static void handle_control_message(struct ports_device 
*portdev,
        int err;
 
        cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);
-
        port = find_port_by_id(portdev, cpkt->id);
        if (!port && cpkt->event != VIRTIO_CONSOLE_PORT_ADD) {
                /* No valid header at start of buffer.  Drop it. */
@@ -1326,6 +1336,11 @@ static void handle_control_message(struct ports_device 
*portdev,
                return;
        }
 
+       /*
+        * These are rare initialization-time events that should be
+        * serialized.
+        */
+       mutex_lock(&virtio_console_mutex);
        switch (cpkt->event) {
        case VIRTIO_CONSOLE_PORT_ADD:
                if (port) {
@@ -1429,6 +1444,7 @@ static void handle_control_message(struct ports_device 
*portdev,
                }
                break;
        }
+       mutex_unlock(&virtio_console_mutex);
 }
 
 static void control_work_handler(struct work_struct *work)
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 7430bc3..03ff6ed 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -29,8 +29,9 @@
 #include <linux/kernel.h>
 #include <linux/kthread.h>
 #include <linux/list.h>
-#include <linux/module.h>
 #include <linux/major.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/sysrq.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
@@ -84,6 +85,10 @@ static LIST_HEAD(hvc_structs);
  * list traversal.
  */
 static DEFINE_SPINLOCK(hvc_structs_lock);
+/*
+ * only one task does allocation at a time.
+ */
+static DEFINE_MUTEX(hvc_ports_mutex);
 
 /*
  * This value is used to assign a tty->index value to a hvc_struct based
@@ -242,6 +247,7 @@ static void destroy_hvc_struct(struct kref *kref)
 
        spin_unlock(&hvc_structs_lock);
 
+       kfree(hp->hvc_console);
        kfree(hp);
 }
 
@@ -822,19 +828,25 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
                             int outbuf_size)
 {
        struct hvc_struct *hp;
+       struct console *cp;
        int i;
 
        /* We wait until a driver actually comes along */
+       mutex_lock(&hvc_ports_mutex);
        if (!hvc_driver) {
                int err = hvc_init();
-               if (err)
+               if (err) {
+                       mutex_unlock(&hvc_ports_mutex);
                        return ERR_PTR(err);
+               }
        }
 
        hp = kzalloc(ALIGN(sizeof(*hp), sizeof(long)) + outbuf_size,
                        GFP_KERNEL);
-       if (!hp)
+       if (!hp) {
+               mutex_unlock(&hvc_ports_mutex);
                return ERR_PTR(-ENOMEM);
+       }
 
        hp->vtermno = vtermno;
        hp->data = data;
@@ -845,6 +857,19 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
        kref_init(&hp->kref);
 
        INIT_WORK(&hp->tty_resize, hvc_set_winsz);
+       /*
+        * make each console its own struct console.
+        * No need to do allocation and copy under lock.
+        */
+       cp = kzalloc(sizeof(*cp), GFP_KERNEL);
+       if (!cp) {
+               kfree(hp);
+               mutex_unlock(&hvc_ports_mutex);
+               return ERR_PTR(-ENOMEM);
+       }
+       memcpy(cp, &hvc_console, sizeof(*cp));
+       hp->hvc_console = cp;
+
        spin_lock_init(&hp->lock);
        spin_lock(&hvc_structs_lock);
 
@@ -862,13 +887,14 @@ struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
                i = ++last_hvc;
 
        hp->index = i;
-       hvc_console.index = i;
+       cp->index = i;
        vtermnos[i] = vtermno;
        cons_ops[i] = ops;
 
        list_add_tail(&(hp->next), &hvc_structs);
        spin_unlock(&hvc_structs_lock);
-       register_console(&hvc_console);
+       register_console(cp);
+       mutex_unlock(&hvc_ports_mutex);
 
        return hp;
 }
@@ -879,7 +905,8 @@ int hvc_remove(struct hvc_struct *hp)
        unsigned long flags;
        struct tty_struct *tty;
 
-       unregister_console(&hvc_console);
+       BUG_ON(!hp->hvc_console);
+       unregister_console(hp->hvc_console);
        spin_lock_irqsave(&hp->lock, flags);
        tty = tty_kref_get(hp->tty);
 
diff --git a/drivers/tty/hvc/hvc_console.h b/drivers/tty/hvc/hvc_console.h
index c335a14..2d20ab7 100644
--- a/drivers/tty/hvc/hvc_console.h
+++ b/drivers/tty/hvc/hvc_console.h
@@ -58,6 +58,7 @@ struct hvc_struct {
        const struct hv_ops *ops;
        int irq_requested;
        int data;
+       struct console *hvc_console;
        struct winsize ws;
        struct work_struct tty_resize;
        struct list_head next;
-- 
1.7.3.1


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