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Commit 411cf9ee authored by Oren Twaig's avatar Oren Twaig Committed by H. Peter Anvin
Browse files

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



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.

Acked-by: default avatarShai Fultheim <shai@scalemp.com>
Signed-off-by: default avatarOren Twaig <oren@scalemp.com>
Link: http://lkml.kernel.org/r/1404036068-11674-1-git-send-email-oren@scalemp.com


Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent b81975ea

arch/x86/include/asm/apic.h

+0 −8
Original line number Diff line number Diff line
@@ -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
Original line number Diff line number Diff line
@@ -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