[edk2-devel] [PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex first before lock cmpxchg

[edk2-devel] [PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex first before lock cmpxchg

[Wu, Jiaxin]

This patch is to check BspIndex first before lock cmpxchg operation.
It's the optimization to lower the resource contention caused by the
atomic compare exchange operation, so as to improve the SMI
performance for BSP election.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Zeng Star <star.zeng@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Kinney Michael D <michael.d.kinney@intel.com>
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
index e988ce0542..085aa91286 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -1652,15 +1652,17 @@ SmiRendezvous (
             }
           } else {
             //
             // Platform hook fails to determine, use default BSP election method
             //
-            InterlockedCompareExchange32 (
-              (UINT32 *)&mSmmMpSyncData->BspIndex,
-              (UINT32)-1,
-              (UINT32)CpuIndex
-              );
+            if (mSmmMpSyncData->BspIndex == MAX_UINT32) {
+              InterlockedCompareExchange32 (
+                (UINT32 *)&mSmmMpSyncData->BspIndex,
+                MAX_UINT32,
+                (UINT32)CpuIndex
+                );
+            }
           }
         }
       }
 
       //
-- 
2.16.2.windows.1



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[edk2-devel] [PATCH v2 0/2] SMM CPU Optimization

[Wu, Jiaxin]

Refine the commit log.

Jiaxin Wu (2):
  UefiCpuPkg/PiSmmCpuDxeSmm: Execute CET and XD check only on BSP
  UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex first before lock cmpxchg

 UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c      | 12 +++--
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c |  6 +--
 UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.c     | 78 +++++++++++++++++-------------
 UefiCpuPkg/PiSmmCpuDxeSmm/SmmProfile.h     |  6 ++-
 4 files changed, 59 insertions(+), 43 deletions(-)

-- 
2.16.2.windows.1



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[edk2-devel] [PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex first before lock cmpxchg

[Wu, Jiaxin]

This patch is to check BspIndex first before lock cmpxchg operation.
If BspIndex has not been set, then do the lock cmpxchg, otherwise,
the APs don't need to lock cmpxchg the BspIndex value since the BSP
election has been done. It's the optimization to lower the resource
contention caused by the atomic compare exchange operation, so as to
improve the SMI performance for BSP election.

Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Zeng Star <star.zeng@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Cc: Kinney Michael D <michael.d.kinney@intel.com>
Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
index e988ce0542..085aa91286 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
@@ -1652,15 +1652,17 @@ SmiRendezvous (
             }
           } else {
             //
             // Platform hook fails to determine, use default BSP election method
             //
-            InterlockedCompareExchange32 (
-              (UINT32 *)&mSmmMpSyncData->BspIndex,
-              (UINT32)-1,
-              (UINT32)CpuIndex
-              );
+            if (mSmmMpSyncData->BspIndex == MAX_UINT32) {
+              InterlockedCompareExchange32 (
+                (UINT32 *)&mSmmMpSyncData->BspIndex,
+                MAX_UINT32,
+                (UINT32)CpuIndex
+                );
+            }
           }
         }
       }
 
       //
-- 
2.16.2.windows.1



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Re: [edk2-devel] [PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex first before lock cmpxchg

[Ni, Ray]

Jiaxin,
Can you separate the changes in 2 patches?
1 is to change (UINT32)-1 to MAX_UINT32, the other is to add the test before test-and-set.

Thanks,
Ray
> -----Original Message-----
> From: Wu, Jiaxin <jiaxin.wu@intel.com>
> Sent: Sunday, February 4, 2024 4:48 PM
> To: devel@edk2.groups.io
> Cc: Ni, Ray <ray.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>; Dong,
> Eric <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>; Gerd
> Hoffmann <kraxel@redhat.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>;
> Kinney, Michael D <michael.d.kinney@intel.com>
> Subject: [PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex
> first before lock cmpxchg
> 
> This patch is to check BspIndex first before lock cmpxchg operation.
> If BspIndex has not been set, then do the lock cmpxchg, otherwise,
> the APs don't need to lock cmpxchg the BspIndex value since the BSP
> election has been done. It's the optimization to lower the resource
> contention caused by the atomic compare exchange operation, so as to
> improve the SMI performance for BSP election.
> 
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Zeng Star <star.zeng@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Kinney Michael D <michael.d.kinney@intel.com>
> Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index e988ce0542..085aa91286 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -1652,15 +1652,17 @@ SmiRendezvous (
>              }
>            } else {
>              //
>              // Platform hook fails to determine, use default BSP election
> method
>              //
> -            InterlockedCompareExchange32 (
> -              (UINT32 *)&mSmmMpSyncData->BspIndex,
> -              (UINT32)-1,
> -              (UINT32)CpuIndex
> -              );
> +            if (mSmmMpSyncData->BspIndex == MAX_UINT32) {
> +              InterlockedCompareExchange32 (
> +                (UINT32 *)&mSmmMpSyncData->BspIndex,
> +                MAX_UINT32,
> +                (UINT32)CpuIndex
> +                );
> +            }
>            }
>          }
>        }
> 
>        //
> --
> 2.16.2.windows.1



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Re: [edk2-devel] [PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex first before lock cmpxchg

[Laszlo Ersek]

On 2/5/24 06:06, Ni, Ray wrote:
> Jiaxin,
> Can you separate the changes in 2 patches?
> 1 is to change (UINT32)-1 to MAX_UINT32, the other is to add the test before test-and-set.

Thanks; I'll defer to Ray on this series.

Laszlo

> 
> Thanks,
> Ray
>> -----Original Message-----
>> From: Wu, Jiaxin <jiaxin.wu@intel.com>
>> Sent: Sunday, February 4, 2024 4:48 PM
>> To: devel@edk2.groups.io
>> Cc: Ni, Ray <ray.ni@intel.com>; Laszlo Ersek <lersek@redhat.com>; Dong,
>> Eric <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>; Gerd
>> Hoffmann <kraxel@redhat.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>;
>> Kinney, Michael D <michael.d.kinney@intel.com>
>> Subject: [PATCH v2 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Check BspIndex
>> first before lock cmpxchg
>>
>> This patch is to check BspIndex first before lock cmpxchg operation.
>> If BspIndex has not been set, then do the lock cmpxchg, otherwise,
>> the APs don't need to lock cmpxchg the BspIndex value since the BSP
>> election has been done. It's the optimization to lower the resource
>> contention caused by the atomic compare exchange operation, so as to
>> improve the SMI performance for BSP election.
>>
>> Cc: Ray Ni <ray.ni@intel.com>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Cc: Eric Dong <eric.dong@intel.com>
>> Cc: Zeng Star <star.zeng@intel.com>
>> Cc: Gerd Hoffmann <kraxel@redhat.com>
>> Cc: Rahul Kumar <rahul1.kumar@intel.com>
>> Cc: Kinney Michael D <michael.d.kinney@intel.com>
>> Signed-off-by: Jiaxin Wu <jiaxin.wu@intel.com>
>> ---
>>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c | 12 +++++++-----
>>  1 file changed, 7 insertions(+), 5 deletions(-)
>>
>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>> b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>> index e988ce0542..085aa91286 100644
>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
>> @@ -1652,15 +1652,17 @@ SmiRendezvous (
>>              }
>>            } else {
>>              //
>>              // Platform hook fails to determine, use default BSP election
>> method
>>              //
>> -            InterlockedCompareExchange32 (
>> -              (UINT32 *)&mSmmMpSyncData->BspIndex,
>> -              (UINT32)-1,
>> -              (UINT32)CpuIndex
>> -              );
>> +            if (mSmmMpSyncData->BspIndex == MAX_UINT32) {
>> +              InterlockedCompareExchange32 (
>> +                (UINT32 *)&mSmmMpSyncData->BspIndex,
>> +                MAX_UINT32,
>> +                (UINT32)CpuIndex
>> +                );
>> +            }
>>            }
>>          }
>>        }
>>
>>        //
>> --
>> 2.16.2.windows.1
> 



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