linux-kernel - Re: [PATCH v7 06/20] x86/virt/tdx: Shut down TDX module in case of error

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Date:   Tue, 22 Nov 2022 17:52:10 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Dave Hansen <dave.hansen@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Kai Huang <kai.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, seanjc@...gle.com, pbonzini@...hat.com,
        dan.j.williams@...el.com, rafael.j.wysocki@...el.com,
        kirill.shutemov@...ux.intel.com, ying.huang@...el.com,
        reinette.chatre@...el.com, len.brown@...el.com,
        tony.luck@...el.com, ak@...ux.intel.com, isaku.yamahata@...el.com,
        chao.gao@...el.com, sathyanarayanan.kuppuswamy@...ux.intel.com,
        bagasdotme@...il.com, sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v7 06/20] x86/virt/tdx: Shut down TDX module in case of
 error

On Tue, Nov 22 2022 at 07:20, Dave Hansen wrote:
> On 11/22/22 01:20, Peter Zijlstra wrote:
>> Either the Changelog is broken or this TDX crud is worse crap than I
>> thought possible, because the only way to actually meet that requirement
>> as stated is stop_machine().
>
> I think the changelog is broken.  I don't see anything in the TDX module
> spec about "the SEMACALL can run concurrently on different CPUs".
> Shutdown, as far as I can tell, just requires that the shutdown seamcall
> be run once on each CPU.  Concurrency and ordering don't seem to matter
> at all.

You're right. The 'can concurrently run' thing is for LP.INIT:

4.2.2.
 LP-Scope Initialization: TDH.SYS.LP.INIT

  TDH.SYS.LP.INIT is intended to perform LP-scope, core-scope and
  package-scope initialization of the Intel TDX module. It can be called
  only after TDH.SYS.INIT completes successfully, and it can run
  concurrently on multiple LPs.