[RFC,06/12] console: support multiple serial console simultaneously

Commit Message

Marek Marczykowski-Górecki June 6, 2022, 3:40 a.m. UTC

Previously only one serial console was supported at the same time. Using
console=com1,dbgp,vga silently ignored all but last serial console (in
this case: only dbgp and vga were active).

Fix this by storing not a single sercon_handle, but an array of them, up
to MAX_SERCONS entries. The value of MAX_SERCONS (4) is arbitrary,
inspired by the number of SERHND_IDX values.

Signed-off-by: Marek Marczykowski-Górecki <[e-mail]>
---
 xen/drivers/char/console.c | 58 ++++++++++++++++++++++++++++++---------
 1 file changed, 45 insertions(+), 13 deletions(-)

Patch

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index f9937c5134c0..f576cfdc3b62 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -113,7 +113,9 @@  static char *__read_mostly conring = _conring;
 static uint32_t __read_mostly conring_size = _CONRING_SIZE;
 static uint32_t conringc, conringp;
 
-static int __read_mostly sercon_handle = -1;
+#define MAX_SERCONS 4
+static int __read_mostly sercon_handle[MAX_SERCONS];
+static int __read_mostly nr_sercon_handle = 0;
 
 #ifdef CONFIG_X86
 /* Tristate: 0 disabled, 1 user enabled, -1 default enabled */
@@ -395,9 +397,17 @@  static unsigned int serial_rx_cons, serial_rx_prod;
 
 static void (*serial_steal_fn)(const char *, size_t nr) = early_puts;
 
+/* Redirect any console output to *fn*, if *handle* is configured as a console. */
 int console_steal(int handle, void (*fn)(const char *, size_t nr))
 {
-    if ( (handle == -1) || (handle != sercon_handle) )
+    int i;
+
+    if ( (handle == -1) )
+        return 0;
+    for ( i = 0; i < nr_sercon_handle; i++ )
+        if ( handle == sercon_handle[i] )
+            break;
+    if ( nr_sercon_handle && i == nr_sercon_handle )
         return 0;
 
     if ( serial_steal_fn != NULL )
@@ -415,10 +425,13 @@  void console_giveback(int id)
 
 void console_serial_puts(const char *s, size_t nr)
 {
+    int i;
+
     if ( serial_steal_fn != NULL )
         serial_steal_fn(s, nr);
     else
-        serial_puts(sercon_handle, s, nr);
+        for ( i = 0; i < nr_sercon_handle; i++ )
+            serial_puts(sercon_handle[i], s, nr);
 
     /* Copy all serial output into PV console */
     pv_console_puts(s, nr);
@@ -956,7 +969,7 @@  void guest_printk(const struct domain *d, const char *fmt, ...)
 void __init console_init_preirq(void)
 {
     char *p;
-    int sh;
+    int sh, i;
 
     serial_init_preirq();
 
@@ -977,7 +990,8 @@  void __init console_init_preirq(void)
             continue;
         else if ( (sh = serial_parse_handle(p)) >= 0 )
         {
-            sercon_handle = sh;
+            if ( nr_sercon_handle < MAX_SERCONS )
+                sercon_handle[nr_sercon_handle++] = sh;
             serial_steal_fn = NULL;
         }
         else
@@ -996,7 +1010,8 @@  void __init console_init_preirq(void)
         opt_console_xen = 0;
 #endif
 
-    serial_set_rx_handler(sercon_handle, serial_rx);
+    for ( i = 0; i < nr_sercon_handle; i++ )
+        serial_set_rx_handler(sercon_handle[i], serial_rx);
     pv_console_set_rx_handler(serial_rx);
 
     /* HELLO WORLD --- start-of-day banner text. */
@@ -1014,7 +1029,8 @@  void __init console_init_preirq(void)
 
     if ( opt_sync_console )
     {
-        serial_start_sync(sercon_handle);
+        for ( i = 0; i < nr_sercon_handle; i++ )
+            serial_start_sync(sercon_handle[i]);
         add_taint(TAINT_SYNC_CONSOLE);
         printk("Console output is synchronous.\n");
         warning_add(warning_sync_console);
@@ -1121,13 +1137,19 @@  int __init console_has(const char *device)
 
 void console_start_log_everything(void)
 {
-    serial_start_log_everything(sercon_handle);
+    int i;
+
+    for ( i = 0; i < nr_sercon_handle; i++ )
+        serial_start_log_everything(sercon_handle[i]);
     atomic_inc(&print_everything);
 }
 
 void console_end_log_everything(void)
 {
-    serial_end_log_everything(sercon_handle);
+    int i;
+
+    for ( i = 0; i < nr_sercon_handle; i++ )
+        serial_end_log_everything(sercon_handle[i]);
     atomic_dec(&print_everything);
 }
 
@@ -1149,23 +1171,32 @@  void console_unlock_recursive_irqrestore(unsigned long flags)
 
 void console_force_unlock(void)
 {
+    int i;
+
     watchdog_disable();
     spin_debug_disable();
     spin_lock_init(&console_lock);
-    serial_force_unlock(sercon_handle);
+    for ( i = 0 ; i < nr_sercon_handle ; i++ )
+        serial_force_unlock(sercon_handle[i]);
     console_locks_busted = 1;
     console_start_sync();
 }
 
 void console_start_sync(void)
 {
+    int i;
+
     atomic_inc(&print_everything);
-    serial_start_sync(sercon_handle);
+    for ( i = 0 ; i < nr_sercon_handle ; i++ )
+        serial_start_sync(sercon_handle[i]);
 }
 
 void console_end_sync(void)
 {
-    serial_end_sync(sercon_handle);
+    int i;
+
+    for ( i = 0; i < nr_sercon_handle; i++ )
+        serial_end_sync(sercon_handle[i]);
     atomic_dec(&print_everything);
 }
 
@@ -1291,7 +1322,8 @@  static int suspend_steal_id;
 
 int console_suspend(void)
 {
-    suspend_steal_id = console_steal(sercon_handle, suspend_steal_fn);
+    if ( nr_sercon_handle )
+        suspend_steal_id = console_steal(sercon_handle[0], suspend_steal_fn);
     serial_suspend();
     return 0;
 }