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Date:   Fri, 30 Jun 2023 12:21:41 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Huang, Kai" <kai.huang@intel.com>
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Subject: Re: [PATCH v12 20/22] x86/virt/tdx: Allow SEAMCALL to handle #UD and
 #GP
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On Fri, Jun 30, 2023 at 12:07:00PM +0200, Peter Zijlstra wrote:
> On Thu, Jun 29, 2023 at 10:33:38AM +0000, Huang, Kai wrote:

> > Looking at the later versions of TDX spec (with TD live migration, etc), it
> > seems they are already using R12-R13 as SEAMCALL output:
> > 
> > https://cdrdv2.intel.com/v1/dl/getContent/733579
> 
> Urgh.. I think I read an older versio because I got bleeding eyes from
> all this colour coded crap.
> 
> All this red is unreadable :-( Have they been told about the glories of
> TeX and diff ?
> 
> > E.g., 6.3.15. NEW: TDH.IMPORT.MEM Leaf
> > 
> > It uses R12 and R13 as input.
> 
> 12 and 14. They skipped 13 for some mysterious raisin.

Things like TDH.SERVTD.BIND do use R13.

> But also, 10,11 are frequently used as input with this new stuff, which
> already suggests the setup from your patches is not tenable.


TDG.SERVTD.RD *why* can't they pass that TD_UUID as a pointer? Using *4*
registers like that is quite insane.

TDG.VP.ENTER :-(((( that has b,15,si,di as additional output.

That means there's not a single register left unused. Can we still get
this changed, please?!?