1 files changed, 23 insertions, 3 deletions

diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index 96e02d845716..3b8f9c68ad3c 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -172,12 +172,34 @@ static struct IO_APIC_route_entry ioapic_read_entry(int apic, int pin)
         return eu.entry;
 }
 
+/*
+ * When we write a new IO APIC routing entry, we need to write the high
+ * word first! If the mask bit in the low word is clear, we will enable
+ * the interrupt, and we need to make sure the entry is fully populated
+ * before that happens.
+ */
 static void ioapic_write_entry(int apic, int pin, struct IO_APIC_route_entry e)
 {
         unsigned long flags;
         union entry_union eu;
         eu.entry = e;
         spin_lock_irqsave(&ioapic_lock, flags);
+        io_apic_write(apic, 0x11 + 2*pin, eu.w2);
+        io_apic_write(apic, 0x10 + 2*pin, eu.w1);
+        spin_unlock_irqrestore(&ioapic_lock, flags);
+}
+
+/*
+ * When we mask an IO APIC routing entry, we need to write the low
+ * word first, in order to set the mask bit before we change the
+ * high bits!
+ */
+static void ioapic_mask_entry(int apic, int pin)
+{
+        unsigned long flags;
+        union entry_union eu = { .entry.mask = 1 };
+
+        spin_lock_irqsave(&ioapic_lock, flags);
         io_apic_write(apic, 0x10 + 2*pin, eu.w1);
         io_apic_write(apic, 0x11 + 2*pin, eu.w2);
         spin_unlock_irqrestore(&ioapic_lock, flags);
@@ -302,9 +324,7 @@ static void clear_IO_APIC_pin(unsigned int apic, unsigned int pin)
         /*
          * Disable it in the IO-APIC irq-routing table:
          */
-        memset(&entry, 0, sizeof(entry));
-        entry.mask = 1;
-        ioapic_write_entry(apic, pin, entry);
+        ioapic_mask_entry(apic, pin);
 }
 
 static void clear_IO_APIC (void)