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

["Zeng, Star" <star.zeng@intel.com>]

As I remember UEFI 2.5 clarified this and added EFI_MEMORY_RO was because EFI_MEMORY_WP had been typically used for cache even before UEFI 2.5.

And I do not think this patch should filter out EFI_MEMORY_WP since this patch is to filter out new paging bits caused by 14dde9e903bb9a719ebb8f3381da72b19509bc36 [MdeModulePkg/Core: Fix out-of-sync issue in GCD].


Thanks,
Star
-----Original Message-----
From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org] 
Sent: Thursday, November 16, 2017 5:30 PM
To: Zeng, Star <star.zeng@intel.com>
Cc: Wang, Jian J <jian.j.wang@intel.com>; Laszlo Ersek <lersek@redhat.com>; edk2-devel@lists.01.org; Yao, Jiewen <jiewen.yao@intel.com>
Subject: Re: [edk2] [PATCH v6 1/2] MdeModulePkg/DxeCore: Filter out all paging capabilities

On 16 November 2017 at 09:28, Zeng, Star <star.zeng@intel.com> wrote:
> Ard,
>
> EFI_MEMORY_WP is for cache.
>
> UefiSpec.h
> //
> // Note: UEFI spec 2.5 and following: use EFI_MEMORY_RO as 
> write-protected physical memory // protection attribute. Also, EFI_MEMORY_WP means cacheability attribute.
> //
> #define EFI_MEMORY_WP               0x0000000000001000ULL
>

Yes, but that was a change in v2.5, before that it was a permission attribute. So it should be filtered from the OS visible memory map as well.

> Thanks,
> Star
> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: Thursday, November 16, 2017 5:25 PM
> To: Wang, Jian J <jian.j.wang@intel.com>
> Cc: edk2-devel@lists.01.org; Yao, Jiewen <jiewen.yao@intel.com>; Zeng, 
> Star <star.zeng@intel.com>; Laszlo Ersek <lersek@redhat.com>
> Subject: Re: [PATCH v6 1/2] MdeModulePkg/DxeCore: Filter out all 
> paging capabilities
>
> On 16 November 2017 at 07:26, Jian J Wang <jian.j.wang@intel.com> wrote:
>> 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);
>
> Why is EFI_MEMORY_WP missing here?
>
>> +    MemoryMapStart = NEXT_MEMORY_DESCRIPTOR(MemoryMapStart, Size);  
>> + }
>> +
>>    Status = EFI_SUCCESS;
>>
>>  Done:
>> --
>> 2.14.1.windows.1
>>
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