It does not necessary to be a working area.
We just need a common TEE flag to indicate if the system run in legacy, SEV, or
TDX, right?
thank you!
Yao, Jiewen
> 在 2021年7月28日，下午1:07，Xu, Min M <min.m...@intel.com> 写道：
>
> On July 27, 2021 8:46 PM, Yao, Jiewen wrote:
>> HI Min
>> I agree with Brijesh.
>>
>> The basic rule is: SEV file shall never refer to TDX data structure. TDX file
>> shall never refer to SEV data structure.
>> These code should be isolated clearly.
>>
>> Do we still need that logic if we follow the new pattern?
> I have replied to Brijesh's mail about the concern of the new pattern.
>
> I have some concern in the current pattern:
> ====================
> OneTimeCall PreMainFunctionHookSev
> OneTimeCall PreMainFunctionHookTdx
> MainFunction:
> XXXXXX
> OneTimeCall PostMainFunctionHookSev
> OneTimeCall PostMainFunctionHookTdx
> ====================
> The TEE function need implement a TEE check function (such as IsSev, or
> IsTdx).
>
> Tdx call CPUID(0x21) to determine if it is tdx guest in the very beginning of
> ResetVector. Then 'TDXG' is set
> in TDX_WORK_AREA. SEV does the similar work which call CheckSevFeatures to
> set SEV_ES_WORK_AREA to 1.
>
> After that both TDX and SEV read the above WORK_AREA to check if it is TDX or
> SEV or legacy guest.
>
> In Tdx the access to SEV_ES_WORK_AREA will trigger error because
> SEV_ES_WORK_AREA is *NOT* initialized by host VMM.
> In SEV-SNP I am afraid the access to TDX_WORK_AREA will trigger error too.
>
> I am wondering if TDX and SEV can use the same memory region (for example,
> TEE_WORK_AREA) as the work area?
> So that this work area is guaranteed to be initialized in both TDX and SEV.
> Structure of the TEE_WORK_AREA may
> look like this:
> typedef struct {
> UINT8 Flag[4]; 'TDXG' or 'SEVG' or all-0
> UINT8 Others[];
> } TEE_WORK_AREA;
>>
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