x86: Use dmi check in apic_is_clustered() on 64-bit to mark the TSC unstable

We will have systems with 2 and more sockets 8cores/2thread,
but we treat them as multi chassis - while they could have
a stable TSC domain.

Use DMI check instead.

[ Impact: do not turn possibly stable TSCs off incorrectly ]

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Ravikiran Thirumalai <kiran@scalex86.org>
LKML-Reference: <49F5532A.5000802@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 59 insertions, 27 deletions

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 1386dbec552..28f747d61d7 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2138,31 +2138,14 @@ static void apic_pm_activate(void) { }
 #endif  /* CONFIG_PM */
 
 #ifdef CONFIG_X86_64
-/*
- * apic_is_clustered_box() -- Check if we can expect good TSC
- *
- * Thus far, the major user of this is IBM's Summit2 series:
- *
- * Clustered boxes may have unsynced TSC problems if they are
- * multi-chassis. Use available data to take a good guess.
- * If in doubt, go HPET.
- */
-__cpuinit int apic_is_clustered_box(void)
+
+static int __cpuinit apic_cluster_num(void)
 {
         int i, clusters, zeros;
         unsigned id;
         u16 *bios_cpu_apicid;
         DECLARE_BITMAP(clustermap, NUM_APIC_CLUSTERS);
 
-        /*
-         * there is not this kind of box with AMD CPU yet.
-         * Some AMD box with quadcore cpu and 8 sockets apicid
-         * will be [4, 0x23] or [8, 0x27] could be thought to
-         * vsmp box still need checking...
-         */
-        if ((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) && !is_vsmp_box())
-                return 0;
-
         bios_cpu_apicid = early_per_cpu_ptr(x86_bios_cpu_apicid);
         bitmap_zero(clustermap, NUM_APIC_CLUSTERS);
 
@@ -2198,18 +2181,67 @@ __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 clusters;
+}
+
+static int __cpuinitdata multi_checked;
+static int __cpuinitdata multi;
+
+static int __cpuinit set_multi(const struct dmi_system_id *d)
+{
+        if (multi)
+                return 0;
+        printk(KERN_INFO "APIC: %s detected, Multi Chassis\n", d->ident);
+        multi = 1;
+        return 0;
+}
+
+static const __cpuinitconst struct dmi_system_id multi_dmi_table[] = {
+        {
+                .callback = set_multi,
+                .ident = "IBM System Summit2",
+                .matches = {
+                        DMI_MATCH(DMI_SYS_VENDOR, "IBM"),
+                        DMI_MATCH(DMI_PRODUCT_NAME, "Summit2"),
+                },
+        },
+        {}
+};
+
+static void __cpuinit dmi_check_multi(void)
+{
+        if (multi_checked)
+                return;
+
+        dmi_check_system(multi_dmi_table);
+        multi_checked = 1;
+}
+
+/*
+ * apic_is_clustered_box() -- Check if we can expect good TSC
+ *
+ * Thus far, the major user of this is IBM's Summit2 series:
+ * Clustered boxes may have unsynced TSC problems if they are
+ * multi-chassis.
+ * Use DMI to check them
+ */
+__cpuinit int apic_is_clustered_box(void)
+{
+        dmi_check_multi();
+        if (multi)
                 return 1;
 
+        if (!is_vsmp_box())
+                return 0;
+
         /*
-         * If clusters > 2, then should be multi-chassis.
-         * May have to revisit this when multi-core + hyperthreaded CPUs come
-         * out, but AFAIK this will work even for them.
+         * ScaleMP vSMPowered boxes have one cluster per board and TSCs are
+         * not guaranteed to be synced between boards
          */
-        return (clusters > 2);
+        if (apic_cluster_num() > 1)
+                return 1;
+
+        return 0;
 }
 #endif