[PATCH] UefiCpuPkg/DxeMpLib: Remove sizeof() that is not necessary

[PATCH] UefiCpuPkg/DxeMpLib: Remove sizeof() that is not necessary

[Jeff Fan]

Reported at https://lists.01.org/pipermail/edk2-devel/2016-November/004685.html

Reported-by: Laszlo Ersek <lersek@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/DxeMpLib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
index 7f3900b..dcc9134 100644
--- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
+++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
@@ -311,7 +311,7 @@ InitMpGlobalData (
   Status  = gBS->AllocatePages (
                    AllocateMaxAddress,
                    EfiReservedMemoryType,
-                   EFI_SIZE_TO_PAGES (sizeof (CpuMpData->AddressMap.RelocateApLoopFuncSize)),
+                   EFI_SIZE_TO_PAGES (CpuMpData->AddressMap.RelocateApLoopFuncSize),
                    &Address
                    );
   ASSERT_EFI_ERROR (Status);
-- 
2.9.3.windows.2

[PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Jeff Fan]

The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It will cause
S3 resume failure.

Adding *volatile* could make sure compiler does not so such optimization.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
index 3fb6864..f13ff3e 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
@@ -55,7 +55,7 @@ AsmGetAddressMap (
 #define LEGACY_REGION_BASE    (0xA0000 - LEGACY_REGION_SIZE)
 
 ACPI_CPU_DATA                mAcpiCpuData;
-UINT32                       mNumberToFinish;
+volatile UINT32              mNumberToFinish;
 MP_CPU_EXCHANGE_INFO         *mExchangeInfo;
 BOOLEAN                      mRestoreSmmConfigurationInS3 = FALSE;
 VOID                         *mGdtForAp = NULL;
@@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
   //
   // Count down the number with lock mechanism.
   //
-  InterlockedDecrement (&mNumberToFinish);
+  InterlockedDecrement ((UINT32 *) &mNumberToFinish);
 }
 
 /**
@@ -406,7 +406,7 @@ MPRendezvousProcedure (
   TopOfStack  = (UINT32) (UINTN) Stack + sizeof (Stack);
   TopOfStack &= ~(UINT32) (CPU_STACK_ALIGNMENT - 1);
   CopyMem ((VOID *) (UINTN) mApHltLoopCode, mApHltLoopCodeTemplate, sizeof (mApHltLoopCodeTemplate));
-  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, &mNumberToFinish);
+  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, (UINT32 *) &mNumberToFinish);
 }
 
 /**
-- 
2.9.3.windows.2

[PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Free SmramRanges to save SMM space

[Jeff Fan]

Cc: Zeng Star <star.zeng@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
index 852b5c7..5f13446 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.c
@@ -1004,6 +1004,7 @@ FindSmramInfo (
     }
   } while (Found);
 
+  FreePool (SmramRanges);
   DEBUG ((EFI_D_INFO, "SMRR Base: 0x%x, SMRR Size: 0x%x\n", *SmrrBase, *SmrrSize));
 }
 
-- 
2.9.3.windows.2

[PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Jeff Fan]

The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It will cause
S3 resume failure.

Adding *volatile* could make sure compiler does not so such optimization.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Feng Tian <feng.tian@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jeff Fan <jeff.fan@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
index 3fb6864..f13ff3e 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
@@ -55,7 +55,7 @@ AsmGetAddressMap (
 #define LEGACY_REGION_BASE    (0xA0000 - LEGACY_REGION_SIZE)
 
 ACPI_CPU_DATA                mAcpiCpuData;
-UINT32                       mNumberToFinish;
+volatile UINT32              mNumberToFinish;
 MP_CPU_EXCHANGE_INFO         *mExchangeInfo;
 BOOLEAN                      mRestoreSmmConfigurationInS3 = FALSE;
 VOID                         *mGdtForAp = NULL;
@@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
   //
   // Count down the number with lock mechanism.
   //
-  InterlockedDecrement (&mNumberToFinish);
+  InterlockedDecrement ((UINT32 *) &mNumberToFinish);
 }
 
 /**
@@ -406,7 +406,7 @@ MPRendezvousProcedure (
   TopOfStack  = (UINT32) (UINTN) Stack + sizeof (Stack);
   TopOfStack &= ~(UINT32) (CPU_STACK_ALIGNMENT - 1);
   CopyMem ((VOID *) (UINTN) mApHltLoopCode, mApHltLoopCodeTemplate, sizeof (mApHltLoopCodeTemplate));
-  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, &mNumberToFinish);
+  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, (UINT32 *) &mNumberToFinish);
 }
 
 /**
-- 
2.9.3.windows.2

Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Laszlo Ersek]

On 11/15/16 03:18, Jeff Fan wrote:
> The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It will cause
> S3 resume failure.
> 
> Adding *volatile* could make sure compiler does not so such optimization.
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Feng Tian <feng.tian@intel.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jeff Fan <jeff.fan@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> index 3fb6864..f13ff3e 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> @@ -55,7 +55,7 @@ AsmGetAddressMap (
>  #define LEGACY_REGION_BASE    (0xA0000 - LEGACY_REGION_SIZE)
>  
>  ACPI_CPU_DATA                mAcpiCpuData;
> -UINT32                       mNumberToFinish;
> +volatile UINT32              mNumberToFinish;
>  MP_CPU_EXCHANGE_INFO         *mExchangeInfo;
>  BOOLEAN                      mRestoreSmmConfigurationInS3 = FALSE;
>  VOID                         *mGdtForAp = NULL;
> @@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
>    //
>    // Count down the number with lock mechanism.
>    //
> -  InterlockedDecrement (&mNumberToFinish);
> +  InterlockedDecrement ((UINT32 *) &mNumberToFinish);
>  }
>  
>  /**
> @@ -406,7 +406,7 @@ MPRendezvousProcedure (
>    TopOfStack  = (UINT32) (UINTN) Stack + sizeof (Stack);
>    TopOfStack &= ~(UINT32) (CPU_STACK_ALIGNMENT - 1);
>    CopyMem ((VOID *) (UINTN) mApHltLoopCode, mApHltLoopCodeTemplate, sizeof (mApHltLoopCodeTemplate));
> -  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, &mNumberToFinish);
> +  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, (UINT32 *) &mNumberToFinish);
>  }
>  
>  /**
> 

I think I understand the idea, but the current solution requires you to
cast away "volatile" in two places. That's not nice, normally it is
undefined behavior.

I recommend to extend this patch, with more patches: please change the
prototype of TransferApToSafeState() so that it takes a pointer-to-volatile.

I also suggest to change the prototype of InterlockedDecrement(). (You
won't have to update all other call sites: it is fine to take/access a
non-volatile object as a volatile, but not the other way around.)

I agree this increases the scope of the patch quite a bit, so maybe
others should chime in as well.

Thanks!
Laszlo

Re: [PATCH] UefiCpuPkg/DxeMpLib: Remove sizeof() that is not necessary

[Laszlo Ersek]

On 11/15/16 03:18, Jeff Fan wrote:
> Reported at https://lists.01.org/pipermail/edk2-devel/2016-November/004685.html
> 
> Reported-by: Laszlo Ersek <lersek@redhat.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Feng Tian <feng.tian@intel.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jeff Fan <jeff.fan@intel.com>
> ---
>  UefiCpuPkg/Library/MpInitLib/DxeMpLib.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> index 7f3900b..dcc9134 100644
> --- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> @@ -311,7 +311,7 @@ InitMpGlobalData (
>    Status  = gBS->AllocatePages (
>                     AllocateMaxAddress,
>                     EfiReservedMemoryType,
> -                   EFI_SIZE_TO_PAGES (sizeof (CpuMpData->AddressMap.RelocateApLoopFuncSize)),
> +                   EFI_SIZE_TO_PAGES (CpuMpData->AddressMap.RelocateApLoopFuncSize),
>                     &Address
>                     );
>    ASSERT_EFI_ERROR (Status);
> 

Looks good to me; the RelocateApLoopFuncSize field even has type UINTN,
which is what EFI_SIZE_TO_PAGES wants.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks!
Laszlo

Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Fan, Jeff]

Laszlo,

I agree to separate another patch to change the prototype of TransferApToSafeState() to reduce one cast operation. I will create v2 for it.

I also agree updating prototype of InterlockedDecrement() is compatible updating. But there are other 5 APIs as blow:
InterlockedIncrement()
InterlockedCompareExchange16()
InterlockedCompareExchange32()
InterlockedCompareExchange64()
InterlockedCompareExchangePointer()

To be consistence, we may need to update them together. 

Liming & MIke, any comments on this updating.

Thanks!
Jeff

-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com] 
Sent: Tuesday, November 15, 2016 10:27 AM
To: Fan, Jeff; edk2-devel@ml01.01.org
Cc: Paolo Bonzini; Yao, Jiewen; Tian, Feng; Kinney, Michael D
Subject: Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

On 11/15/16 03:18, Jeff Fan wrote:
> The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It 
> will cause
> S3 resume failure.
> 
> Adding *volatile* could make sure compiler does not so such optimization.
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Feng Tian <feng.tian@intel.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jeff Fan <jeff.fan@intel.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c 
> b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> index 3fb6864..f13ff3e 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> @@ -55,7 +55,7 @@ AsmGetAddressMap (
>  #define LEGACY_REGION_BASE    (0xA0000 - LEGACY_REGION_SIZE)
>  
>  ACPI_CPU_DATA                mAcpiCpuData;
> -UINT32                       mNumberToFinish;
> +volatile UINT32              mNumberToFinish;
>  MP_CPU_EXCHANGE_INFO         *mExchangeInfo;
>  BOOLEAN                      mRestoreSmmConfigurationInS3 = FALSE;
>  VOID                         *mGdtForAp = NULL;
> @@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
>    //
>    // Count down the number with lock mechanism.
>    //
> -  InterlockedDecrement (&mNumberToFinish);
> +  InterlockedDecrement ((UINT32 *) &mNumberToFinish);
>  }
>  
>  /**
> @@ -406,7 +406,7 @@ MPRendezvousProcedure (
>    TopOfStack  = (UINT32) (UINTN) Stack + sizeof (Stack);
>    TopOfStack &= ~(UINT32) (CPU_STACK_ALIGNMENT - 1);
>    CopyMem ((VOID *) (UINTN) mApHltLoopCode, mApHltLoopCodeTemplate, 
> sizeof (mApHltLoopCodeTemplate));
> -  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, 
> &mNumberToFinish);
> +  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, 
> + (UINT32 *) &mNumberToFinish);
>  }
>  
>  /**
> 

I think I understand the idea, but the current solution requires you to cast away "volatile" in two places. That's not nice, normally it is undefined behavior.

I recommend to extend this patch, with more patches: please change the prototype of TransferApToSafeState() so that it takes a pointer-to-volatile.

I also suggest to change the prototype of InterlockedDecrement(). (You won't have to update all other call sites: it is fine to take/access a non-volatile object as a volatile, but not the other way around.)

I agree this increases the scope of the patch quite a bit, so maybe others should chime in as well.

Thanks!
Laszlo

Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Gao, Liming]

Jeff:
  From those API design point, does they expect the input parameter is volatile? If yes, I agree this change.

Thanks
Liming
From: Fan, Jeff
Sent: Tuesday, November 15, 2016 11:03 AM
To: Laszlo Ersek <lersek@redhat.com>; edk2-devel@ml01.01.org
Cc: Paolo Bonzini <pbonzini@redhat.com>; Yao, Jiewen <jiewen.yao@intel.com>; Tian, Feng <feng.tian@intel.com>; Kinney, Michael D <michael.d.kinney@intel.com>; Gao, Liming <liming.gao@intel.com>
Subject: RE: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

Laszlo,

I agree to separate another patch to change the prototype of TransferApToSafeState() to reduce one cast operation. I will create v2 for it.

I also agree updating prototype of InterlockedDecrement() is compatible updating. But there are other 5 APIs as blow:
InterlockedIncrement()
InterlockedCompareExchange16()
InterlockedCompareExchange32()
InterlockedCompareExchange64()
InterlockedCompareExchangePointer()

To be consistence, we may need to update them together.

Liming & MIke, any comments on this updating.

Thanks!
Jeff

-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com]
Sent: Tuesday, November 15, 2016 10:27 AM
To: Fan, Jeff; edk2-devel@ml01.01.org<mailto:edk2-devel@ml01.01.org>
Cc: Paolo Bonzini; Yao, Jiewen; Tian, Feng; Kinney, Michael D
Subject: Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

On 11/15/16 03:18, Jeff Fan wrote:
> The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It
> will cause
> S3 resume failure.
>
> Adding *volatile* could make sure compiler does not so such optimization.
>
> Cc: Paolo Bonzini
> Cc: Laszlo Ersek
> Cc: Jiewen Yao
> Cc: Feng Tian
> Cc: Michael D Kinney
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jeff Fan
> ---
> UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> index 3fb6864..f13ff3e 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> @@ -55,7 +55,7 @@ AsmGetAddressMap (
> #define LEGACY_REGION_BASE (0xA0000 - LEGACY_REGION_SIZE)
>
> ACPI_CPU_DATA mAcpiCpuData;
> -UINT32 mNumberToFinish;
> +volatile UINT32 mNumberToFinish;
> MP_CPU_EXCHANGE_INFO *mExchangeInfo;
> BOOLEAN mRestoreSmmConfigurationInS3 = FALSE;
> VOID *mGdtForAp = NULL;
> @@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
> //
> // Count down the number with lock mechanism.
> //
> - InterlockedDecrement (&mNumberToFinish);
> + InterlockedDecrement ((UINT32 *) &mNumberToFinish);
> }
>
> /**
> @@ -406,7 +406,7 @@ MPRendezvousProcedure (
> TopOfStack = (UINT32) (UINTN) Stack + sizeof (Stack);
> TopOfStack &= ~(UINT32) (CPU_STACK_ALIGNMENT - 1);
> CopyMem ((VOID *) (UINTN) mApHltLoopCode, mApHltLoopCodeTemplate,
> sizeof (mApHltLoopCodeTemplate));
> - TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack,
> &mNumberToFinish);
> + TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack,
> + (UINT32 *) &mNumberToFinish);
> }
>
> /**
>

I think I understand the idea, but the current solution requires you to cast away "volatile" in two places. That's not nice, normally it is undefined behavior.

I recommend to extend this patch, with more patches: please change the prototype of TransferApToSafeState() so that it takes a pointer-to-volatile.

I also suggest to change the prototype of InterlockedDecrement(). (You won't have to update all other call sites: it is fine to take/access a non-volatile object as a volatile, but not the other way around.)

I agree this increases the scope of the patch quite a bit, so maybe others should chime in as well.

Thanks!
Laszlo

Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Fan, Jeff]

Liming,

I think so. Some internal functions in MdePkg\Library\BaseSynchronizationLib is just using volatile for input parameter. For example,

UINT32
EFIAPI
InternalSyncIncrement (
  IN      volatile UINT32           *Value
  );

Thanks!
Jeff

From: Gao, Liming
Sent: Tuesday, November 15, 2016 6:49 PM
To: Fan, Jeff; Laszlo Ersek; edk2-devel@ml01.01.org
Cc: Paolo Bonzini; Yao, Jiewen; Tian, Feng; Kinney, Michael D
Subject: RE: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

Jeff:
  From those API design point, does they expect the input parameter is volatile? If yes, I agree this change.

Thanks
Liming
From: Fan, Jeff
Sent: Tuesday, November 15, 2016 11:03 AM
To: Laszlo Ersek <lersek@redhat.com<mailto:lersek@redhat.com>>; edk2-devel@ml01.01.org<mailto:edk2-devel@ml01.01.org>
Cc: Paolo Bonzini <pbonzini@redhat.com<mailto:pbonzini@redhat.com>>; Yao, Jiewen <jiewen.yao@intel.com<mailto:jiewen.yao@intel.com>>; Tian, Feng <feng.tian@intel.com<mailto:feng.tian@intel.com>>; Kinney, Michael D <michael.d.kinney@intel.com<mailto:michael.d.kinney@intel.com>>; Gao, Liming <liming.gao@intel.com<mailto:liming.gao@intel.com>>
Subject: RE: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

Laszlo,

I agree to separate another patch to change the prototype of TransferApToSafeState() to reduce one cast operation. I will create v2 for it.

I also agree updating prototype of InterlockedDecrement() is compatible updating. But there are other 5 APIs as blow:
InterlockedIncrement()
InterlockedCompareExchange16()
InterlockedCompareExchange32()
InterlockedCompareExchange64()
InterlockedCompareExchangePointer()

To be consistence, we may need to update them together.

Liming & MIke, any comments on this updating.

Thanks!
Jeff

-----Original Message-----
From: Laszlo Ersek [mailto:lersek@redhat.com]
Sent: Tuesday, November 15, 2016 10:27 AM
To: Fan, Jeff; edk2-devel@ml01.01.org<mailto:edk2-devel@ml01.01.org>
Cc: Paolo Bonzini; Yao, Jiewen; Tian, Feng; Kinney, Michael D
Subject: Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

On 11/15/16 03:18, Jeff Fan wrote:
> The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It
> will cause
> S3 resume failure.
>
> Adding *volatile* could make sure compiler does not so such optimization.
>
> Cc: Paolo Bonzini
> Cc: Laszlo Ersek
> Cc: Jiewen Yao
> Cc: Feng Tian
> Cc: Michael D Kinney
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Jeff Fan
> ---
> UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> index 3fb6864..f13ff3e 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
> @@ -55,7 +55,7 @@ AsmGetAddressMap (
> #define LEGACY_REGION_BASE (0xA0000 - LEGACY_REGION_SIZE)
>
> ACPI_CPU_DATA mAcpiCpuData;
> -UINT32 mNumberToFinish;
> +volatile UINT32 mNumberToFinish;
> MP_CPU_EXCHANGE_INFO *mExchangeInfo;
> BOOLEAN mRestoreSmmConfigurationInS3 = FALSE;
> VOID *mGdtForAp = NULL;
> @@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
> //
> // Count down the number with lock mechanism.
> //
> - InterlockedDecrement (&mNumberToFinish);
> + InterlockedDecrement ((UINT32 *) &mNumberToFinish);
> }
>
> /**
> @@ -406,7 +406,7 @@ MPRendezvousProcedure (
> TopOfStack = (UINT32) (UINTN) Stack + sizeof (Stack);
> TopOfStack &= ~(UINT32) (CPU_STACK_ALIGNMENT - 1);
> CopyMem ((VOID *) (UINTN) mApHltLoopCode, mApHltLoopCodeTemplate,
> sizeof (mApHltLoopCodeTemplate));
> - TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack,
> &mNumberToFinish);
> + TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack,
> + (UINT32 *) &mNumberToFinish);
> }
>
> /**
>

I think I understand the idea, but the current solution requires you to cast away "volatile" in two places. That's not nice, normally it is undefined behavior.

I recommend to extend this patch, with more patches: please change the prototype of TransferApToSafeState() so that it takes a pointer-to-volatile.

I also suggest to change the prototype of InterlockedDecrement(). (You won't have to update all other call sites: it is fine to take/access a non-volatile object as a volatile, but not the other way around.)

I agree this increases the scope of the patch quite a bit, so maybe others should chime in as well.

Thanks!
Laszlo

Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish

[Laszlo Ersek]

On 11/15/16 04:02, Fan, Jeff wrote:
> Laszlo,
> 
> I agree to separate another patch to change the prototype of TransferApToSafeState() to reduce one cast operation. I will create v2 for it.
> 
> I also agree updating prototype of InterlockedDecrement() is compatible updating. But there are other 5 APIs as blow:
> InterlockedIncrement()
> InterlockedCompareExchange16()
> InterlockedCompareExchange32()
> InterlockedCompareExchange64()
> InterlockedCompareExchangePointer()
> 
> To be consistence, we may need to update them together. 

I agree. I didn't know the full list of Interlocked*() APIs off-hand,
but I expected there would be several such functions, and for
consistency they should indeed be updated together. I'm not sure if
everyone agrees with this, hence discussion is welcome.

> 
> Liming & MIke, any comments on this updating.

Yes, please comment!

Thanks
Laszlo

> 
> Thanks!
> Jeff
> 
> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com] 
> Sent: Tuesday, November 15, 2016 10:27 AM
> To: Fan, Jeff; edk2-devel@ml01.01.org
> Cc: Paolo Bonzini; Yao, Jiewen; Tian, Feng; Kinney, Michael D
> Subject: Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Add volatile for mNumberToFinish
> 
> On 11/15/16 03:18, Jeff Fan wrote:
>> The GCC 5.4 will optimize mNumberToFinish in EarlyInitializeCpu(). It 
>> will cause
>> S3 resume failure.
>>
>> Adding *volatile* could make sure compiler does not so such optimization.
>>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Laszlo Ersek <lersek@redhat.com>
>> Cc: Jiewen Yao <jiewen.yao@intel.com>
>> Cc: Feng Tian <feng.tian@intel.com>
>> Cc: Michael D Kinney <michael.d.kinney@intel.com>
>> Contributed-under: TianoCore Contribution Agreement 1.0
>> Signed-off-by: Jeff Fan <jeff.fan@intel.com>
>> ---
>>  UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c 
>> b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
>> index 3fb6864..f13ff3e 100644
>> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
>> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/CpuS3.c
>> @@ -55,7 +55,7 @@ AsmGetAddressMap (
>>  #define LEGACY_REGION_BASE    (0xA0000 - LEGACY_REGION_SIZE)
>>  
>>  ACPI_CPU_DATA                mAcpiCpuData;
>> -UINT32                       mNumberToFinish;
>> +volatile UINT32              mNumberToFinish;
>>  MP_CPU_EXCHANGE_INFO         *mExchangeInfo;
>>  BOOLEAN                      mRestoreSmmConfigurationInS3 = FALSE;
>>  VOID                         *mGdtForAp = NULL;
>> @@ -371,7 +371,7 @@ EarlyMPRendezvousProcedure (
>>    //
>>    // Count down the number with lock mechanism.
>>    //
>> -  InterlockedDecrement (&mNumberToFinish);
>> +  InterlockedDecrement ((UINT32 *) &mNumberToFinish);
>>  }
>>  
>>  /**
>> @@ -406,7 +406,7 @@ MPRendezvousProcedure (
>>    TopOfStack  = (UINT32) (UINTN) Stack + sizeof (Stack);
>>    TopOfStack &= ~(UINT32) (CPU_STACK_ALIGNMENT - 1);
>>    CopyMem ((VOID *) (UINTN) mApHltLoopCode, mApHltLoopCodeTemplate, 
>> sizeof (mApHltLoopCodeTemplate));
>> -  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, 
>> &mNumberToFinish);
>> +  TransferApToSafeState ((UINT32) (UINTN) mApHltLoopCode, TopOfStack, 
>> + (UINT32 *) &mNumberToFinish);
>>  }
>>  
>>  /**
>>
> 
> I think I understand the idea, but the current solution requires you to cast away "volatile" in two places. That's not nice, normally it is undefined behavior.
> 
> I recommend to extend this patch, with more patches: please change the prototype of TransferApToSafeState() so that it takes a pointer-to-volatile.
> 
> I also suggest to change the prototype of InterlockedDecrement(). (You won't have to update all other call sites: it is fine to take/access a non-volatile object as a volatile, but not the other way around.)
> 
> I agree this increases the scope of the patch quite a bit, so maybe others should chime in as well.
> 
> Thanks!
> Laszlo
>