[Xen-changelog] [xen-unstable] x86: On CPU shutdown, clear pending FPU exceptions.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1204626830 0
# Node ID 017927162815139a0b31f7ce5705e9d8bc886945
# Parent  771c7124bf3869493023b78450da71a236debddf
x86: On CPU shutdown, clear pending FPU exceptions.
I've seen at least one BIOS which fails warm reboot if FPU exceptions
are pending.
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/arch/x86/smp.c |   18 ++++++++++++++----
 1 files changed, 14 insertions(+), 4 deletions(-)

diff -r 771c7124bf38 -r 017927162815 xen/arch/x86/smp.c
--- a/xen/arch/x86/smp.c        Tue Mar 04 10:32:13 2008 +0000
+++ b/xen/arch/x86/smp.c        Tue Mar 04 10:33:50 2008 +0000
@@ -306,15 +306,26 @@ int on_selected_cpus(
     return 0;
 }
 
-static void stop_this_cpu (void *dummy)
+static void __stop_this_cpu(void)
 {
     ASSERT(!local_irq_is_enabled());
 
     disable_local_APIC();
+
     hvm_cpu_down();
 
+    /*
+     * Clear FPU, zapping any pending exceptions. Needed for warm reset with
+     * some BIOSes.
+     */
+    clts();
+    asm volatile ( "fninit" );
+}
+
+static void stop_this_cpu(void *dummy)
+{
+    __stop_this_cpu();
     cpu_clear(smp_processor_id(), cpu_online_map);
-
     for ( ; ; )
         halt();
 }
@@ -334,9 +345,8 @@ void smp_send_stop(void)
         mdelay(1);
 
     local_irq_disable();
-    disable_local_APIC();
+    __stop_this_cpu();
     disable_IO_APIC();
-    hvm_cpu_down();
     local_irq_enable();
 }
 

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