Re: [PATCH V2 8/9] MdeModulePkg/Variable: Add RT GetNextVariableName() cache support

["Wu, Hao A" <hao.a.wu@intel.com>]

> -----Original Message-----
> From: Kubacki, Michael A
> Sent: Saturday, September 28, 2019 9:47 AM
> To: devel@edk2.groups.io
> Cc: Bi, Dandan; Ard Biesheuvel; Dong, Eric; Laszlo Ersek; Gao, Liming; Kinney,
> Michael D; Ni, Ray; Wang, Jian J; Wu, Hao A; Yao, Jiewen
> Subject: [PATCH V2 8/9] MdeModulePkg/Variable: Add RT
> GetNextVariableName() cache support
> 
> https://bugzilla.tianocore.org/show_bug.cgi?id=2220
> 
> This change implements the Runtime Service GetNextVariableName()
> using the Runtime Cache in VariableSmmRuntimeDxe. Runtime Service
> calls to GetNextVariableName() will no longer trigger a SW SMI.
> 
> Overall system performance and stability will be improved by
> eliminating an SMI for these calls as they typically result in a
> relatively large number of invocations to retrieve all variable
> names in all variable stores present.
> 
> Cc: Dandan Bi <dandan.bi@intel.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Signed-off-by: Michael Kubacki <michael.a.kubacki@intel.com>
> ---
> 
> MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeDxe
> .c | 118 +++++++++-----------
>  1 file changed, 50 insertions(+), 68 deletions(-)
> 
> diff --git
> a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeD
> xe.c
> b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeD
> xe.c
> index 46f69765a4..bc3b56b0ce 100644
> ---
> a/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeD
> xe.c
> +++
> b/MdeModulePkg/Universal/Variable/RuntimeDxe/VariableSmmRuntimeD
> xe.c
> @@ -799,87 +799,69 @@ RuntimeServiceGetNextVariableName (
>    IN OUT  EFI_GUID                          *VendorGuid
>    )
>  {
> -  EFI_STATUS                                      Status;
> -  UINTN                                           PayloadSize;
> -  SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME
> *SmmGetNextVariableName;
> -  UINTN                                           OutVariableNameSize;
> -  UINTN                                           InVariableNameSize;
> +  EFI_STATUS              Status;
> +  UINTN                   DelayIndex;
> +  UINTN                   MaxLen;
> +  UINTN                   VarNameSize;
> +  VARIABLE_HEADER         *VariablePtr;
> +  VARIABLE_STORE_HEADER
> *VariableStoreHeader[VariableStoreTypeMax];
> +
> +  Status = EFI_NOT_FOUND;
> 
>    if (VariableNameSize == NULL || VariableName == NULL || VendorGuid ==
> NULL) {
>      return EFI_INVALID_PARAMETER;
>    }
> 
> -  OutVariableNameSize   = *VariableNameSize;
> -  InVariableNameSize    = StrSize (VariableName);
> -  SmmGetNextVariableName = NULL;
> -
>    //
> -  // If input string exceeds SMM payload limit. Return failure
> +  // Calculate the possible maximum length of name string, including the
> Null terminator.
>    //
> -  if (InVariableNameSize > mVariableBufferPayloadSize - OFFSET_OF
> (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name)) {
> +  MaxLen = *VariableNameSize / sizeof (CHAR16);
> +  if ((MaxLen == 0) || (StrnLenS (VariableName, MaxLen) == MaxLen)) {
> +    //
> +    // Null-terminator is not found in the first VariableNameSize bytes of the
> input VariableName buffer,
> +    // follow spec to return EFI_INVALID_PARAMETER.
> +    //
>      return EFI_INVALID_PARAMETER;
>    }
> 
> -  AcquireLockOnlyAtBootTime(&mVariableServicesLock);
> +  AcquireLockOnlyAtBootTime (&mVariableServicesLock);
> 
> -  //
> -  // Init the communicate buffer. The buffer data size is:
> -  // SMM_COMMUNICATE_HEADER_SIZE +
> SMM_VARIABLE_COMMUNICATE_HEADER_SIZE + PayloadSize.
> -  //
> -  if (OutVariableNameSize > mVariableBufferPayloadSize - OFFSET_OF
> (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name)) {
> -    //
> -    // If output buffer exceed SMM payload limit. Trim output buffer to SMM
> payload size
> -    //
> -    OutVariableNameSize = mVariableBufferPayloadSize - OFFSET_OF
> (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name);
> +  for (DelayIndex = 0; mVariableRuntimeCacheReadLock && DelayIndex <
> VARIABLE_RT_CACHE_READ_LOCK_TIMEOUT; DelayIndex++) {
> +    MicroSecondDelay (10);
>    }
> -  //
> -  // Payload should be Guid + NameSize + MAX of Input & Output buffer
> -  //
> -  PayloadSize = OFFSET_OF
> (SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME, Name) +
> MAX (OutVariableNameSize, InVariableNameSize);
> -
> -  Status = InitCommunicateBuffer ((VOID **)&SmmGetNextVariableName,
> PayloadSize, SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME);
> -  if (EFI_ERROR (Status)) {
> -    goto Done;
> -  }
> -  ASSERT (SmmGetNextVariableName != NULL);
> -
> -  //
> -  // SMM comm buffer->NameSize is buffer size for return string
> -  //
> -  SmmGetNextVariableName->NameSize = OutVariableNameSize;
> -
> -  CopyGuid (&SmmGetNextVariableName->Guid, VendorGuid);
> -  //
> -  // Copy whole string
> -  //
> -  CopyMem (SmmGetNextVariableName->Name, VariableName,
> InVariableNameSize);
> -  if (OutVariableNameSize > InVariableNameSize) {
> -    ZeroMem ((UINT8 *) SmmGetNextVariableName->Name +
> InVariableNameSize, OutVariableNameSize - InVariableNameSize);
> -  }
> -
> -  //
> -  // Send data to SMM
> -  //
> -  Status = SendCommunicateBuffer (PayloadSize);
> -
> -  //
> -  // Get data from SMM.
> -  //
> -  if (Status == EFI_SUCCESS || Status == EFI_BUFFER_TOO_SMALL) {
> -    //
> -    // SMM CommBuffer NameSize can be a trimed value
> -    // Only update VariableNameSize when needed
> -    //
> -    *VariableNameSize = SmmGetNextVariableName->NameSize;
> -  }
> -  if (EFI_ERROR (Status)) {
> -    goto Done;
> +  if (DelayIndex < VARIABLE_RT_CACHE_READ_LOCK_TIMEOUT) {
> +    ASSERT (!mVariableRuntimeCacheReadLock);
> +
> +    CheckForRuntimeCacheSync ();
> +    mVariableRuntimeCacheReadLock = TRUE;
> +
> +    if (!mVariableRuntimeCachePendingUpdate) {
> +      //
> +      // 0: Volatile, 1: HOB, 2: Non-Volatile.
> +      // The index and attributes mapping must be kept in this order as
> FindVariable
> +      // makes use of this mapping to implement search algorithm.
> +      //
> +      VariableStoreHeader[VariableStoreTypeVolatile] =
> mVariableRuntimeVolatileCacheBuffer;
> +      VariableStoreHeader[VariableStoreTypeHob]      =
> mVariableRuntimeHobCacheBuffer;
> +      VariableStoreHeader[VariableStoreTypeNv]       =
> mVariableRuntimeNvCacheBuffer;
> +
> +      Status = GetNextVariableEx (VariableName, VendorGuid,
> VariableStoreHeader, &VariablePtr);
> +      if (!EFI_ERROR (Status)) {
> +        VarNameSize = NameSizeOfVariable (VariablePtr);
> +        ASSERT (VarNameSize != 0);
> +        if (VarNameSize <= *VariableNameSize) {
> +          CopyMem (VariableName, GetVariableNamePtr (VariablePtr),
> VarNameSize);
> +          CopyMem (VendorGuid, GetVendorGuidPtr (VariablePtr), sizeof
> (EFI_GUID));
> +          Status = EFI_SUCCESS;
> +        } else {
> +          Status = EFI_BUFFER_TOO_SMALL;
> +        }
> +
> +        *VariableNameSize = VarNameSize;
> +      }
> +    }
>    }
> -
> -  CopyGuid (VendorGuid, &SmmGetNextVariableName->Guid);
> -  CopyMem (VariableName, SmmGetNextVariableName->Name,
> SmmGetNextVariableName->NameSize);
> -
> -Done:
> +  mVariableRuntimeCacheReadLock = FALSE;


Similar to the previous patch (7/9),
if timeout occurs when acquiring the read lock, should this flag be set to FALSE
in such case?

Best Regards,
Hao Wu


>    ReleaseLockOnlyAtBootTime (&mVariableServicesLock);
>    return Status;
>  }
> --
> 2.16.2.windows.1