linux-kernel - Re: [PATCH v19 023/130] KVM: TDX: Initialize the TDX module when loading the KVM intel kernel module

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Date: Wed, 8 May 2024 09:59:46 +1200
From: "Huang, Kai" <kai.huang@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: "Zhang, Tina" <tina.zhang@...el.com>, "Yuan, Hang" <hang.yuan@...el.com>,
	"Chen, Bo2" <chen.bo@...el.com>, "sagis@...gle.com" <sagis@...gle.com>,
	"isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Aktas, Erdem"
	<erdemaktas@...gle.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>, "isaku.yamahata@...ux.intel.com"
	<isaku.yamahata@...ux.intel.com>
Subject: Re: [PATCH v19 023/130] KVM: TDX: Initialize the TDX module when
 loading the KVM intel kernel module



On 8/05/2024 4:24 am, Sean Christopherson wrote:
> On Tue, May 07, 2024, Kai Huang wrote:
>>>> So I think we have consensus to go with the approach that shows in your
>>>> second diff -- that is to always enable virtualization during module loading
>>>> for all other ARCHs other than x86, for which we only always enables
>>>> virtualization during module loading for TDX.
>>>
>>> Assuming the other arch maintainers are ok with that approach.  If waiting until
>>> a VM is created is desirable for other architectures, then we'll need to figure
>>> out a plan b.  E.g. KVM arm64 doesn't support being built as a module, so enabling
>>> hardware during initialization would mean virtualization is enabled for any kernel
>>> that is built with CONFIG_KVM=y.
>>>
>>> Actually, duh.  There's absolutely no reason to force other architectures to
>>> choose when to enable virtualization.  As evidenced by the massaging to have x86
>>> keep enabling virtualization on-demand for !TDX, the cleanups don't come from
>>> enabling virtualization during module load, they come from registering cpuup and
>>> syscore ops when virtualization is enabled.
>>>
>>> I.e. we can keep kvm_usage_count in common code, and just do exactly what I
>>> proposed for kvm_x86_enable_virtualization().
>>>
>>> I have patches to do this, and initial testing suggests they aren't wildly
>>> broken.  I'll post them soon-ish, assuming nothing pops up in testing.  They are
>>> clean enough that they can land in advance of TDX, e.g. in kvm-coco-queue even
>>> before other architectures verify I didn't break them.
>>>
>>
>> Hi Sean,
>>
>> Just want to check with you what is your plan on this?
>>
>> Please feel free to let me know if there's anything that I can help.
> 
> Ah shoot, I posted patches[*] but managed to forget to Cc any of the TDX folks.
> Sorry :-/
> 
> [*] https://lore.kernel.org/all/20240425233951.3344485-1-seanjc@google.com

Oh I missed that :-( Thanks for the info!