Re: [PATCH v6 1/2] MdeModulePkg/DxeCore: Filter out all paging capabilities

["Yao, Jiewen" <jiewen.yao@intel.com>]

HI
I have 2 comments:

1) I do not think we need mention: WORKAROUND.
I suggest we just use "NOTE".

We have similar example before, see MdePkg\Library\BasePeCoffLib\BasePeCoff.c
  //
  // NOTE: Some versions of Linux ELILO for Itanium have an incorrect magic value 
  //       in the PE/COFF Header.  If the MachineType is Itanium(IA64) and the 
  //       Magic value in the OptionalHeader is  EFI_IMAGE_NT_OPTIONAL_HDR32_MAGIC
  //       then override the returned value to EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC
  //

2) I agree with Star. I think we should merge the final result.
The suggestion before is: *Keep current UEFI memory map unchanged.*
Changing it brings lots of risk without validating all UEFI OS.


Thank you
Yao Jiewen


> -----Original Message-----
> From: Wang, Jian J
> Sent: Thursday, November 16, 2017 3:27 PM
> To: edk2-devel@lists.01.org
> Cc: Yao, Jiewen <jiewen.yao@intel.com>; Zeng, Star <star.zeng@intel.com>;
> Laszlo Ersek <lersek@redhat.com>; Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Subject: [PATCH v6 1/2] MdeModulePkg/DxeCore: Filter out all paging capabilities
> 
> Some OSs will treat EFI_MEMORY_DESCRIPTOR.Attribute as really
> set attributes and change memory paging attribute accordingly.
> But current EFI_MEMORY_DESCRIPTOR.Attribute is assigned by
> value from Capabilities in GCD memory map. This might cause
> boot problems. Clearing all paging related capabilities can
> workaround it. The code added in this patch is supposed to
> be removed once the usage of EFI_MEMORY_DESCRIPTOR.Attribute
> is clarified in UEFI spec and adopted by both EDK-II Core and
> all supported OSs.
> 
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> ---
>  MdeModulePkg/Core/Dxe/Mem/Page.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/MdeModulePkg/Core/Dxe/Mem/Page.c
> b/MdeModulePkg/Core/Dxe/Mem/Page.c
> index c9219cc068..783b576e35 100644
> --- a/MdeModulePkg/Core/Dxe/Mem/Page.c
> +++ b/MdeModulePkg/Core/Dxe/Mem/Page.c
> @@ -1829,6 +1829,23 @@ CoreGetMemoryMap (
>    //
>    BufferSize = ((UINT8 *)MemoryMap - (UINT8 *)MemoryMapStart);
> 
> +  //
> +  // WORKAROUND: Some OSs will treat EFI_MEMORY_DESCRIPTOR.Attribute
> as really
> +  //             set attributes and change memory paging attribute
> accordingly.
> +  //             But current EFI_MEMORY_DESCRIPTOR.Attribute is assigned
> by
> +  //             value from Capabilities in GCD memory map. This might
> cause
> +  //             boot problems. Clearing all paging related capabilities can
> +  //             workaround it. Following code is supposed to be removed
> once
> +  //             the usage of EFI_MEMORY_DESCRIPTOR.Attribute is clarified
> in
> +  //             UEFI spec and adopted by both EDK-II Core and all
> supported
> +  //             OSs.
> +  //
> +  while (MemoryMapStart < MemoryMap) {
> +    MemoryMapStart->Attribute &= ~(UINT64)(EFI_MEMORY_RP |
> EFI_MEMORY_RO |
> +                                           EFI_MEMORY_XP);
> +    MemoryMapStart = NEXT_MEMORY_DESCRIPTOR(MemoryMapStart,
> Size);
> +  }
> +
>    Status = EFI_SUCCESS;
> 
>  Done:
> --
> 2.14.1.windows.1