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: Tue, 7 May 2024 09:24:18 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Kai Huang <kai.huang@...el.com>
Cc: Tina Zhang <tina.zhang@...el.com>, Hang Yuan <hang.yuan@...el.com>, 
	Bo2 Chen <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>, Erdem Aktas <erdemaktas@...gle.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "pbonzini@...hat.com" <pbonzini@...hat.com>, 
	Isaku Yamahata <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 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