In preparation for further removal of regs parameters, drop it here. In
the two places where it's actually needed, retrieve IRQ context if
available, or else guest context.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
---
As an alternative to the new boolean parameter, I wonder if we couldn't
special-case the idle vCPU case: It's only there where we would not have
proper context retrievable via guest_cpu_user_regs().
---
v3: Re-base.
v2: New.

--- a/xen/common/keyhandler.c
+++ b/xen/common/keyhandler.c
@@ -73,12 +73,12 @@ static struct keyhandler {
 
 static void cf_check keypress_action(void *unused)
 {
-    handle_keypress(keypress_key, NULL);
+    handle_keypress(keypress_key, true);
 }
 
 static DECLARE_TASKLET(keypress_tasklet, keypress_action, NULL);
 
-void handle_keypress(unsigned char key, struct cpu_user_regs *regs)
+void handle_keypress(unsigned char key, bool need_context)
 {
     struct keyhandler *h;
 
@@ -88,7 +88,7 @@ void handle_keypress(unsigned char key,
     if ( !in_irq() || h->irq_callback )
     {
         console_start_log_everything();
-        h->irq_callback ? h->irq_fn(key, regs) : h->fn(key);
+        h->irq_callback ? h->irq_fn(key, need_context) : h->fn(key);
         console_end_log_everything();
     }
     else
@@ -169,7 +169,7 @@ void cf_check dump_execstate(struct cpu_
 }
 
 static void cf_check dump_registers(
-    unsigned char key, struct cpu_user_regs *regs)
+    unsigned char key, bool need_context)
 {
     unsigned int cpu;
 
@@ -182,8 +182,8 @@ static void cf_check dump_registers(
     cpumask_copy(&dump_execstate_mask, &cpu_online_map);
 
     /* Get local execution state out immediately, in case we get stuck. */
-    if ( regs )
-        dump_execstate(regs);
+    if ( !need_context )
+        dump_execstate(get_irq_regs() ?: guest_cpu_user_regs());
     else
         run_in_exception_handler(dump_execstate);
 
@@ -245,8 +245,7 @@ static void cf_check dump_hwdom_register
     }
 }
 
-static void cf_check reboot_machine(
-    unsigned char key, struct cpu_user_regs *regs)
+static void cf_check reboot_machine(unsigned char key, bool unused)
 {
     printk("'%c' pressed -> rebooting machine\n", key);
     machine_restart(0);
@@ -474,8 +473,7 @@ static void cf_check run_all_nonirq_keyh
 static DECLARE_TASKLET(run_all_keyhandlers_tasklet,
                        run_all_nonirq_keyhandlers, NULL);
 
-static void cf_check run_all_keyhandlers(
-    unsigned char key, struct cpu_user_regs *regs)
+static void cf_check run_all_keyhandlers(unsigned char key, bool need_context)
 {
     struct keyhandler *h;
     unsigned int k;
@@ -491,7 +489,7 @@ static void cf_check run_all_keyhandlers
         if ( !h->irq_fn || !h->diagnostic || !h->irq_callback )
             continue;
         printk("[%c: %s]\n", k, h->desc);
-        h->irq_fn(k, regs);
+        h->irq_fn(k, need_context);
     }
 
     watchdog_enable();
@@ -500,8 +498,7 @@ static void cf_check run_all_keyhandlers
     tasklet_schedule(&run_all_keyhandlers_tasklet);
 }
 
-static void cf_check do_toggle_alt_key(
-    unsigned char key, struct cpu_user_regs *regs)
+static void cf_check do_toggle_alt_key(unsigned char key, bool unused)
 {
     alt_key_handling = !alt_key_handling;
     printk("'%c' pressed -> using %s key handling\n", key,
@@ -566,7 +563,7 @@ void keyhandler_crash_action(enum crash_
         if ( *action == '+' )
             mdelay(10);
         else
-            handle_keypress(*action, NULL);
+            handle_keypress(*action, true);
         action++;
     }
 }
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -134,7 +134,7 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xe
         {
             if ( copy_from_guest_offset(&c, op->u.debug_keys.keys, i, 1) )
                 goto out;
-            handle_keypress(c, guest_cpu_user_regs());
+            handle_keypress(c, false);
         }
         ret = 0;
         copyback = 0;
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -279,7 +279,7 @@ static int *__read_mostly upper_thresh_a
 static int *__read_mostly lower_thresh_adj = &xenlog_lower_thresh;
 static const char *__read_mostly thresh_adj = "standard";
 
-static void cf_check do_toggle_guest(unsigned char key, struct cpu_user_regs *regs)
+static void cf_check do_toggle_guest(unsigned char key, bool unused)
 {
     if ( upper_thresh_adj == &xenlog_upper_thresh )
     {
@@ -306,13 +306,13 @@ static void do_adj_thresh(unsigned char
            loglvl_str(*upper_thresh_adj));
 }
 
-static void cf_check do_inc_thresh(unsigned char key, struct cpu_user_regs *regs)
+static void cf_check do_inc_thresh(unsigned char key, bool unused)
 {
     ++*lower_thresh_adj;
     do_adj_thresh(key);
 }
 
-static void cf_check do_dec_thresh(unsigned char key, struct cpu_user_regs *regs)
+static void cf_check do_dec_thresh(unsigned char key, bool unused)
 {
     if ( *lower_thresh_adj )
         --*lower_thresh_adj;
@@ -531,7 +531,7 @@ static void __serial_rx(char c, struct c
     switch ( console_rx )
     {
     case 0:
-        return handle_keypress(c, regs);
+        return handle_keypress(c, false);
 
     case 1:
         /*
--- a/xen/include/xen/keyhandler.h
+++ b/xen/include/xen/keyhandler.h
@@ -24,9 +24,8 @@ typedef void (keyhandler_fn_t)(unsigned
  *
  * Called in hardirq context with interrupts disabled.
  */
-struct cpu_user_regs;
 typedef void (irq_keyhandler_fn_t)(unsigned char key,
-                                   struct cpu_user_regs *regs);
+                                   bool need_context);
 
 /* Initialize keytable with default handlers. */
 void initialize_keytable(void);
@@ -46,7 +45,7 @@ void register_irq_keyhandler(unsigned ch
                              bool diagnostic);
 
 /* Inject a keypress into the key-handling subsystem. */
-extern void handle_keypress(unsigned char key, struct cpu_user_regs *regs);
+extern void handle_keypress(unsigned char key, bool need_context);
 
 enum crash_reason {
     CRASHREASON_PANIC,