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

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 16 November 2017 at 09:48, Zeng, Star <star.zeng@intel.com> wrote:
> 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].
>

Ah ok. If the bit does not get copied from the GCD map then there is
no need to filter it here.

>
> 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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