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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Dave Hansen <dave.hansen@intel.com>,
        Peter Zijlstra <peterz@infradead.org>
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Subject: Re: [PATCH v7 06/20] x86/virt/tdx: Shut down TDX module in case of
 error
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Date:   Wed, 30 Nov 2022 12:09:31 +0100
Message-ID: <87h6ygu2ac.ffs@tglx>
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On Tue, Nov 29 2022 at 13:40, Dave Hansen wrote:
> On 11/22/22 11:33, Peter Zijlstra wrote:
>> Can we get this limitiation removed and simply let the module throw a
>> wobbly (error) when someone tries and use TDX without that logical CPU
>> having been properly initialized?
>
> It sounds like we can at least punt the limitation away from the OS's
> purview.
>
> There's actually a multi-step process to get a "real" TDX module loaded.
>  There's a fancy ACM (Authenticated Code Module) that's invoked via
> GETSEC[ENTERACCS] and an intermediate module loader.  That dance used to
> be done in the kernel, but we talked the BIOS guys into doing it instead.
>
> I believe these per-logical-CPU checks _can_ also be punted out of the
> TDX module itself and delegated to one of these earlier module loading
> phases that the BIOS drives.
>
> I'm still a _bit_ skeptical that the checks are needed in the first
> place.  But, as long as they're hidden from the OS, I don't see a need
> to be too cranky about it.

Right.

> In the end, we could just plain stop doing the TDH.SYS.LP.INIT code in
> the kernel.

Which in turn makes all the problems we discussed go away.

> Unless someone screams, I'll ask the BIOS and TDX module folks to look
> into this.

Yes, please.

Thanks,

        tglx