[xen staging] xen/console: add comment about external console lock helper

[patchbot@xxxxxxx]

commit 4b60085b6e3f8c3afea88685198bb310c332e90e
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Mar 25 10:49:07 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Mar 25 10:49:07 2024 +0100

    xen/console: add comment about external console lock helper
    
    The current console_lock_recursive_irqsave() implementation is not 
speculation
    safe, however it's only used to prevent interleaved output.  Note this in 
the
    function declaration in order for callers to be aware of the limitation.
    
    No functional change.
    
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/include/xen/console.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/include/xen/console.h b/xen/include/xen/console.h
index 68759862e8..6dfbade3ec 100644
--- a/xen/include/xen/console.h
+++ b/xen/include/xen/console.h
@@ -20,6 +20,7 @@ void console_init_postirq(void);
 void console_endboot(void);
 int console_has(const char *device);
 
+/* Not speculation safe - only used to prevent interleaving of output. */
 unsigned long console_lock_recursive_irqsave(void);
 void console_unlock_recursive_irqrestore(unsigned long flags);
 void console_force_unlock(void);
--
generated by git-patchbot for /home/xen/git/xen.git#staging