Re: [Patch] UefiCpuPkg/S3Resume2Pei: disable paging before creating new page table.

[Laszlo Ersek <lersek@redhat.com>]

On 10/09/18 10:26, Ni, Ruiyu wrote:
> On 10/9/2018 4:09 PM, Laszlo Ersek wrote:
>>>
>>> Two comments:
>>> 1. We'd better not map the PcdCpuStackGuard to paging-enable. Maybe some
>>> other feature also enables the paging in PEI phase but the
>>> PcdCpuStackGuard is FALSE.
>>
>> I think I agree.
>>
>>> 2. When PEI is in 64bit mode, disabling paging may not work because
>>> paging-enable is a must in 64bit mode.
>>
>> I think this case is academic. S3Resume2Pei does not support 64-bit PEI
>> with SMM enabled. This is why we have commit 5133d1f1d297 ("OvmfPkg:
>> replace README fine print about X64 SMM S3 with PlatformPei check",
>> 2015-11-30) in OVMF.
> 
> I found that commit. I just checked S3Resume2Pei module. It does assumes
> it's running in 32bit mode. And CpuS3.c also assumes S3Resume2Pei is
> running in 32bit mode.
> 
>>
>> Anyway, I'm making this comment in the general sense only. I'm not
>> suggesting that we disable paging unconditionally. Actually, I believe,
>> I will suggest (under the v3 posting) restricting the write to CR0 even
>> more.
> Why?

I explained under v3.

Thanks,
Laszlo