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

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Message-ID: <0ddb198c9a8ae72519c3f7847089d84a8de4821f.camel@intel.com>
Date: Tue, 7 May 2024 12:40:33 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "seanjc@...gle.com" <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


> > 
> > 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. 
Thanks.