x86: do_boot_cpu - check if we have ESR register

Impact: fix APIC IRQ irregularities on certain older boxes

We should touch the APIC ESR register if only we have it.

The patch fixes the problem mentioned by Max Kellermann:

	http://lkml.org/lkml/2008/10/17/147

Bisected-by: Max Kellermann <mk@cm4all.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
[ mingo@elte.hu: build fix ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 5 insertions, 3 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 7ece815ea637..7b1093397319 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -893,9 +893,11 @@ do_rest:
                 smpboot_setup_warm_reset_vector(start_ip);
                 /*
                  * Be paranoid about clearing APIC errors.
-                */
-                apic_write(APIC_ESR, 0);
-                apic_read(APIC_ESR);
+                */
+                if (APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid])) {
+                        apic_write(APIC_ESR, 0);
+                        apic_read(APIC_ESR);
+                }
         }
 
         /*