x86: apic_is_clustered_box to indicate unsynched TSC's on multiboard vSMP systems

Indicate TSCs are unreliable as time sources if the platform is
a multi chassi ScaleMP vSMPowered machine.

Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 1 deletions

diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index 868ec1deb19..5362cfd30ec 100644
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -1209,7 +1209,7 @@ __cpuinit int apic_is_clustered_box(void)
          * will be [4, 0x23] or [8, 0x27] could be thought to
          * vsmp box still need checking...
          */
-        if (!is_vsmp_box() && (boot_cpu_data.x86_vendor == X86_VENDOR_AMD))
+        if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && !is_vsmp_box())
                 return 0;
 
         bios_cpu_apicid = x86_bios_cpu_apicid_early_ptr;
@@ -1249,6 +1249,12 @@ __cpuinit int apic_is_clustered_box(void)
                         ++zeros;
         }
 
+        /* ScaleMP vSMPowered boxes have one cluster per board and TSCs are
+         * not guaranteed to be synced between boards
+         */
+        if (is_vsmp_box() && clusters > 1)
+                return 1;
+
         /*
          * If clusters > 2, then should be multi-chassis.
          * May have to revisit this when multi-core + hyperthreaded CPUs come