IO-APIC: Prevent using EOI broadcast suppression if user specified ioapic_ack=new on the command line.

Currently, if EOI broadcast suppression is advertised on the BSP
LAPIC, Xen will discard any user specified option regarding IO-APIC
ack mode.

This patch introduces a check which prevents EOI Broadcast suppression
from forcing the IO-APIC ack mode to old if the user has explicitly
asked for the new ack mode on the command line.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Committed-by: Keir Fraser <keir@xen.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/xen/arch/x86/io_apic.c b/xen/arch/x86/io_apic.c
index 1c8334924a..31f1541aea 100644
--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -44,6 +44,7 @@ static DEFINE_SPINLOCK(ioapic_lock);
 
 bool_t __read_mostly skip_ioapic_setup;
 bool_t __read_mostly ioapic_ack_new = 1;
+bool_t __read_mostly ioapic_ack_forced = 0;
 
 #ifndef sis_apic_bug
 /*
@@ -1543,9 +1544,15 @@ static unsigned int startup_level_ioapic_irq(struct irq_desc *desc)
 static void __init setup_ioapic_ack(char *s)
 {
     if ( !strcmp(s, "old") )
+    {
         ioapic_ack_new = 0;
+        ioapic_ack_forced = 1;
+    }
     else if ( !strcmp(s, "new") )
+    {
         ioapic_ack_new = 1;
+        ioapic_ack_forced = 1;
+    }
     else
         printk("Unknown ioapic_ack value specified: '%s'\n", s);
 }