Even going back to 3.2 source code, I can't spot how this watchdog mode
could ever have been enabled in Xen. The only effect its presence had
for all the years was the retaining of a dead string literal.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/include/asm/apic.h
+++ b/xen/arch/x86/include/asm/apic.h
@@ -186,7 +186,6 @@ extern void check_nmi_watchdog(void);
 
 extern unsigned int nmi_watchdog;
 #define NMI_NONE	0
-#define NMI_IO_APIC	1
-#define NMI_LOCAL_APIC	2
+#define NMI_LOCAL_APIC	1
 
 #endif /* __ASM_APIC_H */
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2004,11 +2004,6 @@ static void __init check_timer(void)
     }
     printk(" failed.\n");
 
-    if (nmi_watchdog == NMI_IO_APIC) {
-        printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI Watchdog!\n");
-        nmi_watchdog = 0;
-    }
-
     printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");
 
     disable_8259A_irq(irq_to_desc(0));

On 25/01/2024 2:13 pm, Jan Beulich wrote:
> Even going back to 3.2 source code, I can't spot how this watchdog mode
> could ever have been enabled in Xen. The only effect its presence had
> for all the years was the retaining of a dead string literal.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

We have far too much junk here.

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>