[PATCH v3 04/24] xen/console: introduce console_{get,put}_domain()

[Denis Mukhin via B4 Relay <devnull+dmukhin.ford.com@xxxxxxxxxx>]

From: Denis Mukhin <dmukhin@xxxxxxxx>

console_input_domain() takes an RCU lock to protect domain structure.
That implies call to rcu_unlock_domain() after use.

Introduce a pair of console_get_domain() / console_put_domain() to highlight
the correct use of the call within the code interacting with Xen console
driver.

Also, use new calls in the console driver in __serial_rx(). That prepares
the code for the follow-on console driver cleanup series.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
 xen/arch/arm/vpl011.c      |  6 +++---
 xen/drivers/char/console.c | 44 +++++++++++++++++++++-----------------------
 xen/include/xen/console.h  |  3 ++-
 3 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c
index 
c72f3778bfedf9434f9d1a0cd7fa33852563112d..66047bf33cedb930a6bd7c96577913cd1ae08f05
 100644
--- a/xen/arch/arm/vpl011.c
+++ b/xen/arch/arm/vpl011.c
@@ -78,7 +78,7 @@ static void vpl011_write_data_xen(struct domain *d, uint8_t 
data)
     unsigned long flags;
     struct vpl011 *vpl011 = &d->arch.vpl011;
     struct vpl011_xen_backend *intf = vpl011->backend.xen;
-    struct domain *input = console_input_domain();
+    struct domain *input = console_get_domain();
 
     VPL011_LOCK(d, flags);
 
@@ -123,8 +123,8 @@ static void vpl011_write_data_xen(struct domain *d, uint8_t 
data)
     vpl011_update_interrupt_status(d);
 
     VPL011_UNLOCK(d, flags);
-    if ( input != NULL )
-        rcu_unlock_domain(input);
+
+    console_put_domain(input);
 }
 
 /*
diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 
1411c991977b5fb26ee5709e523b7bc32b612808..4785f0e93a17e3ecba79a7813d2928f946abab8f
 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -475,15 +475,18 @@ static unsigned int __read_mostly console_rx = 0;
 
 #define max_console_rx (max_init_domid + 1)
 
-#ifdef CONFIG_SBSA_VUART_CONSOLE
-/* Make sure to rcu_unlock_domain after use */
-struct domain *console_input_domain(void)
+struct domain *console_get_domain(void)
 {
     if ( console_rx == 0 )
             return NULL;
     return rcu_lock_domain_by_id(console_rx - 1);
 }
-#endif
+
+void console_put_domain(struct domain *d)
+{
+    if ( d )
+        rcu_unlock_domain(d);
+}
 
 static void switch_serial_input(void)
 {
@@ -529,14 +532,18 @@ static void switch_serial_input(void)
 
 static void __serial_rx(char c)
 {
+    struct domain *d;
     int rc = 0;
 
-    switch ( console_rx )
-    {
-    case 0:
+    if ( console_rx == 0 )
         return handle_keypress(c, false);
 
-    case 1:
+    d = console_get_domain();
+    if ( !d )
+        return;
+
+    if ( is_hardware_domain(d) )
+    {
         /*
          * Deliver input to the hardware domain buffer, unless it is
          * already full.
@@ -549,23 +556,12 @@ static void __serial_rx(char c)
          * getting stuck.
          */
         send_global_virq(VIRQ_CONSOLE);
-        break;
-
+    }
 #ifdef CONFIG_SBSA_VUART_CONSOLE
-    default:
-    {
-        struct domain *d = rcu_lock_domain_by_id(console_rx - 1);
-
-        if ( d )
-        {
-            rc = vpl011_rx_char_xen(d, c);
-            rcu_unlock_domain(d);
-        }
-
-        break;
-    }
+    else
+        /* Deliver input to the emulated UART. */
+        rc = vpl011_rx_char_xen(d, c);
 #endif
-    }
 
 #ifdef CONFIG_X86
     if ( pv_shim && pv_console )
@@ -574,6 +570,8 @@ static void __serial_rx(char c)
 
     if ( rc )
         printk(KERN_ERR "d%pd: failed to process console input: %d\n", d, rc);
+
+    console_put_domain(d);
 }
 
 static void cf_check serial_rx(char c)
diff --git a/xen/include/xen/console.h b/xen/include/xen/console.h
index 
6dfbade3ece36352c74f1124305da945b210f2a7..8631fd279bfe1aba42b61d76fbdb45016c2859f9
 100644
--- a/xen/include/xen/console.h
+++ b/xen/include/xen/console.h
@@ -31,7 +31,8 @@ void console_end_sync(void);
 void console_start_log_everything(void);
 void console_end_log_everything(void);
 
-struct domain *console_input_domain(void);
+struct domain *console_get_domain(void);
+void console_put_domain(struct domain *d);
 
 /*
  * Steal output from the console. Returns +ve identifier, else -ve error.

-- 
2.34.1