[xen master] console: make input work again for pv-shim

[patchbot@xxxxxxx]

commit 698b0f5031c6083401234a9b9415175cc5855a0a
Author:     Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
AuthorDate: Thu Oct 19 09:54:50 2023 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 19 09:54:50 2023 +0200

    console: make input work again for pv-shim
    
    The use of rcu_lock_domain_by_id() right in switch_serial_input() makes
    assumptions about domain IDs which don't hold when in shim mode: The
    sole (initial) domain there has a non-zero ID. Obtain the real domain ID
    in that case (generalized as get_initial_domain_id() returns zero when
    not in shim mode).
    
    Note that console_input_domain() isn't altered, for not being used when
    in shim mode (or more generally on x86).
    
    Fixes: c2581c58bec9 ("xen/console: skip switching serial input to non 
existing domains")
    Signed-off-by: Manuel Bouyer <bouyer@xxxxxxxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>
    Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
---
 xen/drivers/char/console.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/char/console.c b/xen/drivers/char/console.c
index f81b8b6b47..6b679c5eac 100644
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -468,7 +468,7 @@ static void cf_check dump_console_ring_key(unsigned char 
key)
 #define switch_code (opt_conswitch[0]-'a'+1)
 /*
  * console_rx=0 => input to xen
- * console_rx=1 => input to dom0
+ * console_rx=1 => input to dom0 (or the sole shim domain)
  * console_rx=N => input to dom(N-1)
  */
 static unsigned int __read_mostly console_rx = 0;
@@ -493,6 +493,7 @@ static void switch_serial_input(void)
      */
     for ( ; ; )
     {
+        domid_t domid;
         struct domain *d;
 
         if ( next_rx++ >= max_console_rx )
@@ -502,12 +503,18 @@ static void switch_serial_input(void)
             break;
         }
 
-        d = rcu_lock_domain_by_id(next_rx - 1);
+#ifdef CONFIG_PV_SHIM
+        if ( next_rx == 1 )
+            domid = get_initial_domain_id();
+        else
+#endif
+            domid = next_rx - 1;
+        d = rcu_lock_domain_by_id(domid);
         if ( d )
         {
             rcu_unlock_domain(d);
             console_rx = next_rx;
-            printk("*** Serial input to DOM%u", next_rx - 1);
+            printk("*** Serial input to DOM%u", domid);
             break;
         }
     }
--
generated by git-patchbot for /home/xen/git/xen.git#master