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Date:   Wed, 23 Nov 2022 08:41:22 -0800
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Subject: Re: [PATCH v7 06/20] x86/virt/tdx: Shut down TDX module in case of
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To:     Sean Christopherson <seanjc@google.com>,
        "Huang, Kai" <kai.huang@intel.com>
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        "Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
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        "Yamahata, Isaku" <isaku.yamahata@intel.com>,
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        "Huang, Ying" <ying.huang@intel.com>,
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From:   Dave Hansen <dave.hansen@intel.com>
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On 11/23/22 08:20, Sean Christopherson wrote:
>>> Why is it done that way?
>>>
>>> Can it be changed to delay TDX initialization until the first TDX guest
>>> needs to run?
>>>
>> Sean suggested.
>>
>> Hi Sean, could you commenet?
> Waiting until the first TDX guest is created would result in false advertising,
> as KVM wouldn't know whether or not TDX is actually supported until that first
> VM is created.  If we can guarantee that TDH.SYS.INIT will fail if and only if
> there is a kernel bug, then I would be ok deferring the "enabling" until the
> first VM is created.

There's no way we can guarantee _that_.  For one, the PAMT* allocations
can always fail.  I guess we could ask sysadmins to fire up a guest to
"prime" things, but that seems a little silly.  Maybe that would work as
the initial implementation that we merge, but I suspect our users will
demand more determinism, maybe a boot or module parameter.

 * Physical Address Metadata Table, a large physically contiguous data
   structure, the rough equivalent of 'struct page' for the TDX module