Re: [PATCH] UefiCpuPkg/PiSmmCpuDxeSmm: Avoid allocate Token every time

["Laszlo Ersek" <lersek@redhat.com>]

Hi Eric,

I have three comments:

On 12/04/19 09:05, Eric Dong wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2388
> 
> Token is new introduced by MM MP Protocol. Current logic allocate Token
> every time when need to use it. The logic caused SMI latency raised to
> very high. Update logic to allocate Token buffer at driver's entry point.
> Later use the token from the allocated token buffer. Only when all the
> buffer have been used, then need to allocate new buffer.
> 
> Signed-off-by: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> ---
> V3 changes:
>   Introduce PCD to control the pre allocated toke buffer size.
> 
> v2 changes:
>   Minor update based on comments.
> 
>  UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c        | 67 ++++++++++++++++++--
>  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h   | 15 +++++
>  UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf |  1 +
>  UefiCpuPkg/UefiCpuPkg.dec                    |  4 ++
>  UefiCpuPkg/UefiCpuPkg.uni                    |  1 +
>  5 files changed, 84 insertions(+), 4 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> index d8d2b6f444..33aad3f3e9 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/MpService.c
> @@ -492,6 +492,24 @@ FreeTokens (
>  {
>    LIST_ENTRY            *Link;
>    PROCEDURE_TOKEN       *ProcToken;
> +  TOKEN_BUFFER          *TokenBuf;
> +
> +  //
> +  // Not free the buffer, just clear the UsedTokenNum. In order to
> +  // avoid triggering allocate action when we need to use the token,
> +  // do not free the buffer.
> +  //
> +  gSmmCpuPrivate->UsedTokenNum = 0;
> +
> +  Link = GetFirstNode (&gSmmCpuPrivate->OldTokenBufList);
> +  while (!IsNull (&gSmmCpuPrivate->OldTokenBufList, Link)) {
> +    TokenBuf = TOKEN_BUFFER_FROM_LINK (Link);
> +
> +    Link = RemoveEntryList (&TokenBuf->Link);
> +
> +    FreePool (TokenBuf->Buffer);
> +    FreePool (TokenBuf);
> +  }
>  
>    while (!IsListEmpty (&gSmmCpuPrivate->TokenList)) {
>      Link = GetFirstNode (&gSmmCpuPrivate->TokenList);
> @@ -499,7 +517,6 @@ FreeTokens (
>  
>      RemoveEntryList (&ProcToken->Link);
>  
> -    FreePool ((VOID *)ProcToken->ProcedureToken);
>      FreePool (ProcToken);
>    }
>  }
> @@ -1115,13 +1132,37 @@ CreateToken (
>    VOID
>    )
>  {
> -  PROCEDURE_TOKEN    *ProcToken;
> +  PROCEDURE_TOKEN     *ProcToken;
>    SPIN_LOCK           *CpuToken;
>    UINTN               SpinLockSize;
> +  TOKEN_BUFFER        *TokenBuf;
> +  UINT32              TokenCountPerChunk;
>  
>    SpinLockSize = GetSpinLockProperties ();
> -  CpuToken = AllocatePool (SpinLockSize);
> -  ASSERT (CpuToken != NULL);
> +  TokenCountPerChunk = PcdGet32 (PcdTokenCountPerChunk);

(1) I understand that the DEC file introduces the PCD as
[PcdsFixedAtBuild] *only*. So, at this specific time, the code above is
safe.

But I'm worried that at a later time, we might relax that to a dynamic
PCD, and then the above code will behave really badly. Therefore, please
update the patch in one of two ways:

(1a) please use a static global variable in the entry point function to
cache the PCD, and then use that variable in place of the PCD everywhere,

(1b) alternatively, please update the INF file, and the PcdGet32() calls
too, to [FixedPcd] and FixedPcdGet32(). Then, if we happen to relax the
PCD declaration to dynamic, and a platform actually tries to use that,
they will get a build error. (And then they'll be forced to imlement
(1a) above.)

The idea is to make this as robust / safe as possible.

> +
> +  if (gSmmCpuPrivate->UsedTokenNum == TokenCountPerChunk) {
> +    DEBUG ((DEBUG_VERBOSE, "CpuSmm: No free token buffer, allocate new buffer!\n"));
> +
> +    //
> +    // Record current token buffer for later free action usage.
> +    // Current used token buffer not in this list.
> +    //
> +    TokenBuf = AllocatePool (sizeof (TOKEN_BUFFER));
> +    ASSERT (TokenBuf != NULL);
> +    TokenBuf->Signature = TOKEN_BUFFER_SIGNATURE;
> +    TokenBuf->Buffer  = gSmmCpuPrivate->CurrentTokenBuf;
> +
> +    InsertTailList (&gSmmCpuPrivate->OldTokenBufList, &TokenBuf->Link);
> +
> +    gSmmCpuPrivate->CurrentTokenBuf = AllocatePool (SpinLockSize * TokenCountPerChunk);
> +    ASSERT (gSmmCpuPrivate->CurrentTokenBuf != NULL);
> +    gSmmCpuPrivate->UsedTokenNum = 0;
> +  }
> +
> +  CpuToken = (SPIN_LOCK *)(gSmmCpuPrivate->CurrentTokenBuf + SpinLockSize * gSmmCpuPrivate->UsedTokenNum);
> +  gSmmCpuPrivate->UsedTokenNum++;
> +
>    InitializeSpinLock (CpuToken);
>    AcquireSpinLock (CpuToken);
>  
> @@ -1737,10 +1778,28 @@ InitializeDataForMmMp (
>    VOID
>    )
>  {
> +  UINTN              SpinLockSize;
> +  UINT32             TokenCountPerChunk;
> +
> +  SpinLockSize = GetSpinLockProperties ();
> +  TokenCountPerChunk = PcdGet32 (PcdTokenCountPerChunk);
> +  ASSERT_EFI_ERROR (TokenCountPerChunk != 0);
> +  if (TokenCountPerChunk == 0) {
> +    DEBUG ((EFI_D_ERROR, "PcdTokenCountPerChunk should not be Zero!\n"));

(2) This is a good check, but we should use DEBUG_ERROR, not EFI_D_ERROR.

> +    CpuDeadLoop ();
> +  }
> +  DEBUG ((DEBUG_INFO, "CpuSmm: SpinLock Size = 0x%x, PreAllocateTokenNum = 0x%x\n", SpinLockSize, TokenCountPerChunk));
> +
> +  gSmmCpuPrivate->CurrentTokenBuf = AllocatePool (SpinLockSize * TokenCountPerChunk);
> +  ASSERT (gSmmCpuPrivate->CurrentTokenBuf != NULL);
> +
> +  gSmmCpuPrivate->UsedTokenNum = 0;
> +
>    gSmmCpuPrivate->ApWrapperFunc = AllocatePool (sizeof (PROCEDURE_WRAPPER) * gSmmCpuPrivate->SmmCoreEntryContext.NumberOfCpus);
>    ASSERT (gSmmCpuPrivate->ApWrapperFunc != NULL);
>  
>    InitializeListHead (&gSmmCpuPrivate->TokenList);
> +  InitializeListHead (&gSmmCpuPrivate->OldTokenBufList);
>  }
>  
>  /**
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> index 8c29f1a558..08ef8d2e15 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.h
> @@ -217,6 +217,17 @@ typedef struct {
>  
>  #define PROCEDURE_TOKEN_FROM_LINK(a)  CR (a, PROCEDURE_TOKEN, Link, PROCEDURE_TOKEN_SIGNATURE)
>  
> +#define TOKEN_BUFFER_SIGNATURE  SIGNATURE_32 ('T', 'K', 'B', 'S')
> +
> +typedef struct {
> +  UINTN                   Signature;
> +  LIST_ENTRY              Link;
> +
> +  UINT8                   *Buffer;
> +} TOKEN_BUFFER;
> +
> +#define TOKEN_BUFFER_FROM_LINK(a)  CR (a, TOKEN_BUFFER, Link, TOKEN_BUFFER_SIGNATURE)
> +
>  //
>  // Private structure for the SMM CPU module that is stored in DXE Runtime memory
>  // Contains the SMM Configuration Protocols that is produced.
> @@ -243,6 +254,10 @@ typedef struct {
>    PROCEDURE_WRAPPER               *ApWrapperFunc;
>    LIST_ENTRY                      TokenList;
>  
> +  LIST_ENTRY                      OldTokenBufList;
> +
> +  UINT8                           *CurrentTokenBuf;
> +  UINTN                           UsedTokenNum;     // Only record tokens used in CurrentTokenBuf.
>  } SMM_CPU_PRIVATE_DATA;
>  
>  extern SMM_CPU_PRIVATE_DATA  *gSmmCpuPrivate;
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> index 851a8cb258..8b6c71b697 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/PiSmmCpuDxeSmm.inf
> @@ -140,6 +140,7 @@
>    gEfiMdeModulePkgTokenSpaceGuid.PcdNullPointerDetectionPropertyMask    ## CONSUMES
>    gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask               ## CONSUMES
>    gEfiMdePkgTokenSpaceGuid.PcdControlFlowEnforcementPropertyMask        ## CONSUMES
> +  gUefiCpuPkgTokenSpaceGuid.PcdTokenCountPerChunk                       ## CONSUMES
>  
>  [Depex]
>    gEfiMpServiceProtocolGuid
> diff --git a/UefiCpuPkg/UefiCpuPkg.dec b/UefiCpuPkg/UefiCpuPkg.dec
> index 83acd33612..8ec2153459 100644
> --- a/UefiCpuPkg/UefiCpuPkg.dec
> +++ b/UefiCpuPkg/UefiCpuPkg.dec
> @@ -147,6 +147,10 @@
>    # @Prompt Specify size of good stack of exception which need switching stack.
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuKnownGoodStackSize|2048|UINT32|0x30002001
>  
> +  ## Size of pre allocated token count per chunk.
> +  # @Prompt Specify the size of pre allocated token count per chunk.
> +  gUefiCpuPkgTokenSpaceGuid.PcdTokenCountPerChunk|64|UINT32|0x30002002
> +
>  [PcdsFixedAtBuild, PcdsPatchableInModule]
>    ## This value is the CPU Local APIC base address, which aligns the address on a 4-KByte boundary.
>    # @Prompt Configure base address of CPU Local APIC
> diff --git a/UefiCpuPkg/UefiCpuPkg.uni b/UefiCpuPkg/UefiCpuPkg.uni
> index fbf7680726..3bb951cc72 100644
> --- a/UefiCpuPkg/UefiCpuPkg.uni
> +++ b/UefiCpuPkg/UefiCpuPkg.uni
> @@ -252,3 +252,4 @@
>                                                                                              "24000000  -  6th and 7th generation Intel Core processors and Intel Xeon W Processor Family(24MHz).<BR>\n"
>                                                                                              "19200000  -  Intel Atom processors based on Goldmont Microarchitecture with CPUID signature 06_5CH(19.2MHz).<BR>\n"
>  
> +#string STR_gUefiCpuPkgTokenSpaceGuid_PcdTokenCountPerChunk_PROMPT  #language en-US "Specify the size of pre allocated token count per chunk.\n"
> \ No newline at end of file
> 

(3) I think this would be the first PCD in the UNI file that does not
have _HELP, only _PROMPT. Is that OK? It seems like an inconsistency.
But, I'll let Ray decide.

With (1) fixed (either (1a) or (1b)):

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

Thanks
Laszlo