[PATCH] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

[PATCH] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

[Oren Twaig]

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 <oren@scalemp.com>
Acked-by: Shai Fultheim <shai@scalemp.com>
---
 arch/x86/include/asm/apic.h |    8 ------
 arch/x86/kernel/apic/apic.c |   60 +------------------------------------------
 2 files changed, 1 insertion(+), 67 deletions(-)

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
 

Re: [PATCH] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

[Andi Kleen]

On Mon, Jun 23, 2014 at 08:35:14AM +0300, Oren Twaig wrote:
> 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.

Looks good to me. Yes the APIC cluster check is obsolete.

-andi

Re: [PATCH] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

[Oren Twaig]

ping
On 06/23/2014 08:35 AM, Oren Twaig wrote:
> 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 <oren@scalemp.com>
> Acked-by: Shai Fultheim <shai@scalemp.com>
> ---
>  arch/x86/include/asm/apic.h |    8 ------
>  arch/x86/kernel/apic/apic.c |   60 +------------------------------------------
>  2 files changed, 1 insertion(+), 67 deletions(-)
>
> 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
> 
>
>

Re: [PATCH] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

[H. Peter Anvin]

On 06/26/2014 10:05 PM, Oren Twaig wrote:
> 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

Re: [PATCH] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()

[Oren Twaig]

Hi,

There was actually a problem that the mailer which changed a '\t' to spaces.
This is why it conflicted with the tip:x86/apic branch. Any how, I've also
tested on the x86/apic branch and everything is ok.

Sent :
"[PATCH v2] x86, vsmp: Remove is_vsmp_box() from apic_is_clustered_box()"

Sorry for any troubles.

Thanks,
Oren.

On 06/27/2014 08:39 AM, H. Peter Anvin wrote:
> On 06/26/2014 10:05 PM, Oren Twaig wrote:
>> 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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