[PATCH] VirtioConsole support.

From: Miche Baker-Harvey
Date: Thu Oct 27 2011 - 17:44:30 EST

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.

Signed-off-by: Miche Baker-Harvey <miche@xxxxxxxxxx>
Reported-by-and-Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@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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