x86, perf: Unmask LVTPC only if we have APIC supported

Ingo reported:

 |
 | There's a build failure on -tip with the P4 driver, on UP 32-bit, if
 | PERF_EVENTS is enabled but UP_APIC is disabled:
 |
 | arch/x86/built-in.o: In function `p4_pmu_handle_irq':
 | perf_event.c:(.text+0xa756): undefined reference to `apic'
 | perf_event.c:(.text+0xa76e): undefined reference to `apic'
 |

So we have to unmask LVTPC only if we're configured to have one.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Lin Ming <ming.m.lin@intel.com>
CC: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20100313081116.GA5179@lenovo>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_p4.c b/arch/x86/kernel/cpu/perf_event_p4.c
index 381f593e829..ef861da1c8a 100644
--- a/arch/x86/kernel/cpu/perf_event_p4.c
+++ b/arch/x86/kernel/cpu/perf_event_p4.c
@@ -365,8 +365,10 @@ static int p4_pmu_handle_irq(struct pt_regs *regs)
         }
 
         if (handled) {
+#ifdef CONFIG_X86_LOCAL_APIC
                 /* p4 quirk: unmask it again */
                 apic_write(APIC_LVTPC, apic_read(APIC_LVTPC) & ~APIC_LVT_MASKED);
+#endif
                 inc_irq_stat(apic_perf_irqs);
         }