Re: [PATCH] MdeModulePkg/Core: Merge memory map after filtering paging capability

[Laszlo Ersek <lersek@redhat.com>]

Hello Jian,

On 11/27/17 06:34, Jian J Wang wrote:
> Once the paging capabilities were filtered out, there might be some adjacent entries
> sharing the same capabilities. It's recommended to merge those entries for the OS
> compatibility purpose.
> 
> This patch makes use of existing method MergeMemoryMap() to do it. This is done by
> simply turning this method from static to extern, and call it after filter code.
> 
> This patch is related to an issue described at
>    https://bugzilla.tianocore.org/show_bug.cgi?id=753
> 
> This patch is also passed test of booting follow OSs:
>     Windows 10
>     Windows Server 2016
>     Fedora 26
>     Fedora 25
> 
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> ---
>  MdeModulePkg/Core/Dxe/DxeMain.h              | 18 ++++++++++++++++++
>  MdeModulePkg/Core/Dxe/Mem/Page.c             |  1 +
>  MdeModulePkg/Core/Dxe/Misc/PropertiesTable.c |  1 -
>  3 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/MdeModulePkg/Core/Dxe/DxeMain.h b/MdeModulePkg/Core/Dxe/DxeMain.h
> index 1a0babba71..07b86ba696 100644
> --- a/MdeModulePkg/Core/Dxe/DxeMain.h
> +++ b/MdeModulePkg/Core/Dxe/DxeMain.h
> @@ -2948,4 +2948,22 @@ ApplyMemoryProtectionPolicy (
>    IN  UINT64                Length
>    );
>  
> +/**
> +  Merge continous memory map entries whose have same attributes.
> +
> +  @param  MemoryMap       A pointer to the buffer in which firmware places
> +                          the current memory map.
> +  @param  MemoryMapSize   A pointer to the size, in bytes, of the
> +                          MemoryMap buffer. On input, this is the size of
> +                          the current memory map.  On output,
> +                          it is the size of new memory map after merge.
> +  @param  DescriptorSize  Size, in bytes, of an individual EFI_MEMORY_DESCRIPTOR.
> +**/
> +VOID
> +MergeMemoryMap (
> +  IN OUT EFI_MEMORY_DESCRIPTOR  *MemoryMap,
> +  IN OUT UINTN                  *MemoryMapSize,
> +  IN UINTN                      DescriptorSize
> +  );
> +
>  #endif
> diff --git a/MdeModulePkg/Core/Dxe/Mem/Page.c b/MdeModulePkg/Core/Dxe/Mem/Page.c
> index 962ae90d3d..ca4ce69a3f 100644
> --- a/MdeModulePkg/Core/Dxe/Mem/Page.c
> +++ b/MdeModulePkg/Core/Dxe/Mem/Page.c
> @@ -1915,6 +1915,7 @@ CoreGetMemoryMap (
>                                        EFI_MEMORY_XP);
>      MemoryMap = NEXT_MEMORY_DESCRIPTOR (MemoryMap, Size);
>    }
> +  MergeMemoryMap (MemoryMapStart, &BufferSize, Size);
>  
>    Status = EFI_SUCCESS;
>  
> diff --git a/MdeModulePkg/Core/Dxe/Misc/PropertiesTable.c b/MdeModulePkg/Core/Dxe/Misc/PropertiesTable.c
> index 6cf5edcbe5..75d9b14c1f 100644
> --- a/MdeModulePkg/Core/Dxe/Misc/PropertiesTable.c
> +++ b/MdeModulePkg/Core/Dxe/Misc/PropertiesTable.c
> @@ -182,7 +182,6 @@ SortMemoryMap (
>                                   it is the size of new memory map after merge.
>    @param  DescriptorSize         Size, in bytes, of an individual EFI_MEMORY_DESCRIPTOR.
>  **/
> -STATIC
>  VOID
>  MergeMemoryMap (
>    IN OUT EFI_MEMORY_DESCRIPTOR  *MemoryMap,
> 

This patch looks good to me -- I expect merging the memmap can only
collapse more entries into fewer entries, so the repro / test
instructions that I added to the BZ earlier, and the expected OS
behavior should remain unchanged.

I have one small suggestion: like before, I suggest keeping the local
variables up-to-date after adding the new code, so that further code
need not hunt down invariants as a starting step. Therefore, after the
MergeMemoryMap() call, how about updating MemoryMapEnd, like this:

  MemoryMapEnd = (EFI_MEMORY_DESCRIPTOR *)(
                   (UINT8 *)MemoryMapStart + BufferSize
                   );

I think (if Jiewen and Star agree with this suggestion) that you don't
need to post a v2 just for this.

I'm also fine with the patch if the MemoryMapEnd update is rejected.

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

Can you please add a note to TianoCore BZ#753 when you push this?

Thanks!
Laszlo