x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

Remove invalid code which caused TSC to be declared as "unstable" on vSMP Foundation box even if it was stable and let the kernel decide for itself.

When a vSMP Foundation box is detected, the function apic_cluster_num() counts the number of APIC clusters found. If more than one found, a multi board configuration is assumed, and TSC marked as unstable. This behavior is incorrect as vSMP Foundation may use processors from single node only, attached to memory of other nodes - and such node may have more than one APIC cluster (typically any recent intel box has more than single APIC_CLUSTERID(x)).

To fix this, we simply remove the code which detects a vSMP Foundation box and affects apic_is_clusted_box() return value. This can be done because later the kernel checks by itself if the TSC is stable using the check_tsc_sync_[source|target]() functions and marks TSC as unstable if needed.

Remove invalid code which caused TSC to be declared as "unstable" on vSMP Foundation box even if it was stable and let the kernel decide for itself.

When a vSMP Foundation box is detected, the function apic_cluster_num() counts the number of APIC clusters found. If more than one found, a multi board configuration is assumed, and TSC marked as unstable. This behavior is incorrect as vSMP Foundation may use processors from single node only, attached to memory of other nodes - and such node may have more than one APIC cluster (typically any recent intel box has more than single APIC_CLUSTERID(x)).

To fix this, we simply remove the code which detects a vSMP Foundation box and affects apic_is_clusted_box() return value. This can be done because later the kernel checks by itself if the TSC is stable using the check_tsc_sync_[source|target]() functions and marks TSC as unstable if needed.

Signed-off-by Oren Twaig <[email protected]>

Acked-by Shai Fultheim <[email protected]>

---
 arch/x86/include/asm/apic.h |    8 ------
 arch/x86/kernel/apic/apic.c |   60 +------------------------------------------
 2 files changed, 1 insertion(+), 67 deletions(-)

arch/x86/include/asm/apic.h +0 -8

index 19b0eba..c100694 100644
@@ -85,14 +85,6 @@ static inline bool apic_from_smp_config(void)
 #include <asm/paravirt.h>
 #endif
 
-#ifdef CONFIG_X86_64
-extern int is_vsmp_box(void);
-#else
-static inline int is_vsmp_box(void)
-{
-    return 0;
-}
-#endif
 extern int setup_profiling_timer(unsigned int);
 
 static inline void native_apic_mem_write(u32 reg, u32 v)

arch/x86/kernel/apic/apic.c +1 -59

index ad28db7..2b85bb9 100644
@@ -2451,51 +2451,6 @@ static void apic_pm_activate(void) { }
 
 #ifdef CONFIG_X86_64
 
-static int apic_cluster_num(void)
-{
-    int i, clusters, zeros;
-    unsigned id;
-    u16 *bios_cpu_apicid;
-    DECLARE_BITMAP(clustermap, NUM_APIC_CLUSTERS);
-
-    bios_cpu_apicid = early_per_cpu_ptr(x86_bios_cpu_apicid);
-    bitmap_zero(clustermap, NUM_APIC_CLUSTERS);
-
-    for (i = 0; i < nr_cpu_ids; i++) {
-        /* are we being called early in kernel startup? */
-        if (bios_cpu_apicid) {
-            id = bios_cpu_apicid[i];
-        } else if (i < nr_cpu_ids) {
-            if (cpu_present(i))
-                id = per_cpu(x86_bios_cpu_apicid, i);
-            else
-                continue;
-        } else
-            break;
-
-        if (id != BAD_APICID)
-            __set_bit(APIC_CLUSTERID(id), clustermap);
-    }
-
-    /* Problem:  Partially populated chassis may not have CPUs in some of
-     * the APIC clusters they have been allocated.  Only present CPUs have
-     * x86_bios_cpu_apicid entries, thus causing zeroes in the bitmap.
-     * Since clusters are allocated sequentially, count zeros only if
-     * they are bounded by ones.
-     */
-    clusters = 0;
-    zeros = 0;
-    for (i = 0; i < NUM_APIC_CLUSTERS; i++) {
-        if (test_bit(i, clustermap)) {
-            clusters += 1 + zeros;
-            zeros = 0;
-        } else
-            ++zeros;
-    }
-
-    return clusters;
-}
-
 static int multi_checked;
 static int multi;
 

@@ -2540,20 +2495,7 @@ static void dmi_check_multi(void)
 int apic_is_clustered_box(void)
 {
     dmi_check_multi();
-    if (multi)
-        return 1;
-
-    if (!is_vsmp_box())
-        return 0;
-
-    /*
-     * ScaleMP vSMPowered boxes have one cluster per board and TSCs are
-     * not guaranteed to be synced between boards
-     */
-    if (apic_cluster_num() > 1)
-        return 1;
-
-    return 0;
+    return multi;
 }
 #endif
 

ping

Quoted 1 line · Oren Twaig

ping

This patch conflicts with the changes on the tip:x86/apic branch. Could you please rebase the patch on top of that branch?

-hpa

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