Re: [PATCH v3 1/1] x86/fred: Remove ENDBR64 from FRED entry points

[H. Peter Anvin]

On 2025-08-13 14:07, Dave Hansen wrote:
> On 7/15/25 23:33, Xin Li (Intel) wrote:
>> The FRED specification has been changed in v9.0 to state that there
>> is no need for FRED event handlers to begin with ENDBR64, because
>> in the presence of supervisor indirect branch tracking, FRED event
>> delivery does not enter the WAIT_FOR_ENDBRANCH state.
>>
>> As a result, remove ENDBR64 from FRED entry points.
> 
> So, the spec is being updated or has been updated to reflect the new
> architecture, right?
> 
> Remind me, are there no FRED systems out in the wild today, so we don't
> have to worry about breaking anything?

Correct. The FRED v9 spec contains this change.

All production hardware and late pre-production hardware will have this.

	-hpa