Re: [edk2-devel] [PATCH] MdeModulePkg/Variable: Merge variable header + data update into one step

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

+Jiewen (I seem to remember Jiewen co-authored a whitepaper on edk2
variables; I could be wrong)

one more comment below:

On 11/14/23 09:23, Gao wrote:
> REF:https://bugzilla.tianocore.org/show_bug.cgi?id=4597
> 
> When creating a new variable, skip marking VAR_HEADER_VALID_ONLY so that
> variable header + data update can be merged into one flash write. This
> will greatly reduce the time taken for updating a variable and thus
> increase performance. Removing VAR_HEADER_VALID_ONLY marking doesn't
> have any function impact since it's not used by current code to detect
> variable header + data corruption.

That would have been my question; thanks for spelling it out in advance
(in the commit message).

I wouldn't like to start reviewing this right now, but if you don't get
a review in a week or so, feel free to ping me; I'll try to dig into it.

Laszlo

> 
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Cc: Ray Ni <ray.ni@intel.com>
> Signed-off-by: Gao Cheng <gao.cheng@intel.com>
> ---
>  .../Universal/Variable/RuntimeDxe/Variable.c  | 45 ++-----------------
>  1 file changed, 4 insertions(+), 41 deletions(-)
> 
> diff --git a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
> index 7a1331255b..3c360481f4 100644
> --- a/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
> +++ b/MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c
> @@ -2168,11 +2168,9 @@ UpdateVariable (
>  
>      if (!mVariableModuleGlobal->VariableGlobal.EmuNvMode) {
>        //
> -      // Four steps
> -      // 1. Write variable header
> -      // 2. Set variable state to header valid
> -      // 3. Write variable data
> -      // 4. Set variable state to valid
> +      // Two steps
> +      // 1. Write variable header and data
> +      // 2. Set variable state to valid
>        //
>        //
>        // Step 1:
> @@ -2183,7 +2181,7 @@ UpdateVariable (
>                   TRUE,
>                   Fvb,
>                   mVariableModuleGlobal->NonVolatileLastVariableOffset,
> -                 (UINT32)GetVariableHeaderSize (AuthFormat),
> +                 (UINT32)VarSize,
>                   (UINT8 *)NextVariable
>                   );
>  
> @@ -2194,41 +2192,6 @@ UpdateVariable (
>        //
>        // Step 2:
>        //
> -      NextVariable->State = VAR_HEADER_VALID_ONLY;
> -      Status              = UpdateVariableStore (
> -                              &mVariableModuleGlobal->VariableGlobal,
> -                              FALSE,
> -                              TRUE,
> -                              Fvb,
> -                              mVariableModuleGlobal->NonVolatileLastVariableOffset + OFFSET_OF (VARIABLE_HEADER, State),
> -                              sizeof (UINT8),
> -                              &NextVariable->State
> -                              );
> -
> -      if (EFI_ERROR (Status)) {
> -        goto Done;
> -      }
> -
> -      //
> -      // Step 3:
> -      //
> -      Status = UpdateVariableStore (
> -                 &mVariableModuleGlobal->VariableGlobal,
> -                 FALSE,
> -                 TRUE,
> -                 Fvb,
> -                 mVariableModuleGlobal->NonVolatileLastVariableOffset + GetVariableHeaderSize (AuthFormat),
> -                 (UINT32)(VarSize - GetVariableHeaderSize (AuthFormat)),
> -                 (UINT8 *)NextVariable + GetVariableHeaderSize (AuthFormat)
> -                 );
> -
> -      if (EFI_ERROR (Status)) {
> -        goto Done;
> -      }
> -
> -      //
> -      // Step 4:
> -      //
>        NextVariable->State = VAR_ADDED;
>        Status              = UpdateVariableStore (
>                                &mVariableModuleGlobal->VariableGlobal,



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