linux-kernel - Ping: Re: [PATCH v2] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered

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Message-ID: <53C22C8A.2010406@scalemp.com>
Date:	Sun, 13 Jul 2014 09:51:54 +0300
From:	Oren Twaig <oren@...lemp.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Rientjes <rientjes@...gle.com>,
	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@...achi.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Andi Kleen <ak@...ux.intel.com>,
	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	Richard Weinberger <richard@....at>
CC:	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Ping: Re: [PATCH v2] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

ping
On 07/06/2014 09:33 AM, Oren Twaig wrote:
> Hi,
>
> Quick question: As I'm new at this (submitting patches), what is a reasonable
> time to wait before ping-ing a patch ?
>
> Oren.
>
> On 06/29/2014 01:01 PM, Oren Twaig wrote:
>> 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: Shai Fultheim <shai@...lemp.com>
>> Signed-off-by: Oren Twaig <oren@...lemp.com>
>> ---
>> diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
>> index 19b0eba..c100694 100644
>> --- a/arch/x86/include/asm/apic.h
>> +++ b/arch/x86/include/asm/apic.h
>> @@ -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)
>> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
>> index ad28db7..2b85bb9 100644
>> --- a/arch/x86/kernel/apic/apic.c
>> +++ b/arch/x86/kernel/apic/apic.c
>> @@ -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
>>
>>
>
>


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