[PATCH 26/36] xen/console: introduce console_write()

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

From: Denis Mukhin <dmukhin@xxxxxxxx>

PV Linux kernel uses HYPERVISOR_console_io hypercall for early console which
ends up being handled by Xen's console driver's guest_console_write().

guest_console_write() duplicates the code from __putstr(), elimitate code
duplication.

Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
 xen/drivers/char/console.c | 94 ++++++++++++++++++++++++----------------------
 1 file changed, 50 insertions(+), 44 deletions(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index 
4439e00763631969767719053cdc81e67c2cda2c..3d8d3c852e69d8fddd1d978fdd8932eb75551f25
 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -665,6 +665,19 @@ static void cf_check notify_dom0_con_ring(void *unused)
 static DECLARE_SOFTIRQ_TASKLET(notify_dom0_con_ring_tasklet,
                                notify_dom0_con_ring, NULL);
 
+static bool console_locks_busted;
+
+static void conring_write(const char *str, size_t len)
+{
+    if ( opt_console_to_ring )
+    {
+        conring_puts(str, len);
+
+        if ( !console_locks_busted )
+            tasklet_schedule(&notify_dom0_con_ring_tasklet);
+    }
+}
+
 #ifdef CONFIG_X86
 static inline void xen_console_write_debug_port(const char *buf, size_t len)
 {
@@ -673,8 +686,43 @@ static inline void xen_console_write_debug_port(const char 
*buf, size_t len)
                    : "=&S" (tmp), "=&c" (tmp)
                    : "0" (buf), "1" (len), "d" (XEN_HVM_DEBUGCONS_IOPORT) );
 }
+
+static void xen_console_write(const char *str, size_t len)
+{
+    if ( opt_console_xen )
+    {
+        if ( xen_guest )
+            xen_hypercall_console_write(str, len);
+        else
+            xen_console_write_debug_port(str, len);
+    }
+}
+#else
+static void xen_console_write(const char *str, size_t len)
+{
+}
 #endif
 
+/*
+ * Write characters to console.
+ *
+ * That will handle all possible scenarios working w/ console
+ * - serial console;
+ * - video output;
+ * - __HYPERVISOR_console_io hypercall (x86 only);
+ * - debug I/O port (x86 only);
+ * - forward to Xen event channel.
+ */
+static void console_write(const char *str, size_t len)
+{
+    ASSERT(rspin_is_locked(&console_lock));
+
+    console_serial_puts(str, len);
+    video_puts(str, len);
+    xen_console_write(str, len);
+    conring_write(str, len);
+}
+
 static long guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer,
                                 unsigned int count)
 {
@@ -695,28 +743,8 @@ static long 
guest_console_write(XEN_GUEST_HANDLE_PARAM(char) buffer,
 
         if ( is_hardware_domain(cd) )
         {
-            /* Use direct console output as it could be interactive */
             nrspin_lock_irq(&console_lock);
-
-            console_serial_puts(kbuf, kcount);
-            video_puts(kbuf, kcount);
-
-#ifdef CONFIG_X86
-            if ( opt_console_xen )
-            {
-                if ( xen_guest )
-                    xen_hypercall_console_write(kbuf, kcount);
-                else
-                    xen_console_write_debug_port(kbuf, kcount);
-            }
-#endif
-
-            if ( opt_console_to_ring )
-            {
-                conring_puts(kbuf, kcount);
-                tasklet_schedule(&notify_dom0_con_ring_tasklet);
-            }
-
+            console_write(kbuf, kcount);
             nrspin_unlock_irq(&console_lock);
         }
         else
@@ -817,31 +845,9 @@ long do_console_io(
  * *****************************************************
  */
 
-static bool console_locks_busted;
-
 static void __putstr(const char *str)
 {
-    size_t len = strlen(str);
-
-    ASSERT(rspin_is_locked(&console_lock));
-
-    console_serial_puts(str, len);
-    video_puts(str, len);
-
-#ifdef CONFIG_X86
-    if ( opt_console_xen )
-    {
-        if ( xen_guest )
-            xen_hypercall_console_write(str, len);
-        else
-            xen_console_write_debug_port(str, len);
-    }
-#endif
-
-    conring_puts(str, len);
-
-    if ( !console_locks_busted )
-        tasklet_schedule(&notify_dom0_con_ring_tasklet);
+    console_write(str, strlen(str));
 }
 
 static int printk_prefix_check(char *p, char **pp)

-- 
2.34.1