linux-kernel - Re: [PATCH v9 04/18] x86/virt/tdx: Add skeleton to initialize TDX on demand

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Date:   Tue, 14 Feb 2023 13:46:45 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Kai Huang <kai.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, dave.hansen@...el.com, tglx@...utronix.de,
        seanjc@...gle.com, pbonzini@...hat.com, dan.j.williams@...el.com,
        rafael.j.wysocki@...el.com, kirill.shutemov@...ux.intel.com,
        ying.huang@...el.com, reinette.chatre@...el.com,
        len.brown@...el.com, tony.luck@...el.com, ak@...ux.intel.com,
        isaku.yamahata@...el.com, chao.gao@...el.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, david@...hat.com,
        bagasdotme@...il.com, sagis@...gle.com, imammedo@...hat.com
Subject: Re: [PATCH v9 04/18] x86/virt/tdx: Add skeleton to initialize TDX on
 demand

On Tue, Feb 14, 2023 at 12:59:11AM +1300, Kai Huang wrote:
> Use a state machine protected by mutex to make sure the initialization
> will only be done once, as tdx_enable() can be called multiple times
> (i.e. KVM module can be reloaded) and be called concurrently by other
> kernel components in the future.

I still object to doing tdx_enable() at kvm module load.

kvm.ko gets loaded unconditionally on boot, even if I then never use
kvm.

This stuff needs to be done when an actual VM is created, not before.