Re: [edk2-devel] [Patch V4] UefiCpuPkg/MpInitLib: Enable execute disable bit.

["Laszlo Ersek" <lersek@redhat.com>]

On 11/17/23 08:01, Ni, Ray wrote:
> Laszlo,
> I agree that the BSP's XD status is saved in both CpuMpData and
> ExchangeInfo.
> But, thinking from another perspective, ExchangeInfo is "only" used by
> the assembly
> code. That's why the BSP code needs to save the XD status in CpuMpData
> and ExchangeInfo.
> 
> If we remove the XD status field in ExchangeInfo, then the assembly code
> has to understand
> the structure layout of CpuMpData, which is what I prefer to avoid.
> 
> If you compare all fields in ExchangeInfo and CpuMpData, following
> fields are already duplicated:
> * CpuMpData.CpuInfoHob <-> MpExchangeInfo.CpuInfo
> * InitFlag
> * SevEsIsEnabled
> * SevSnpIsEnabled
> * GhcbBase
> 
> 
> So, I prefer to keep the current change proposed in Yuanhao's patch.

Very good explanation, thank you.

Can we perhaps document, in an additional patch:

- in "UefiCpuPkg/Library/MpInitLib/MpEqu.inc", that the assembly
routines are not supposed to access the internals of CPU_MP_DATA,

- the same statement above "struct _CPU_MP_DATA" in
"UefiCpuPkg/Library/MpInitLib/MpLib.h"?

A number of structures in "UefiCpuPkg/Library/MpInitLib/MpLib.h"
document whether they are to be used by assembly code vs. C code (vs.
both), but CPU_MP_DATA doesn't seem to have such comments.

For the current patch:

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

Thanks!
Laszlo



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