linux-kernel - Re: [PATCH v9 07/18] x86/virt/tdx: Do TDX module per-cpu initialization

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Message-ID: <e04d07c83b2bae4d89ba6c70d857cdf14cef8387.camel@intel.com>
Date:   Tue, 14 Feb 2023 00:09:05 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "Luck, Tony" <tony.luck@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "Gao, Chao" <chao.gao@...el.com>,
        "Brown, Len" <len.brown@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Subject: Re: [PATCH v9 07/18] x86/virt/tdx: Do TDX module per-cpu
 initialization

On Mon, 2023-02-13 at 15:52 -0800, Dave Hansen wrote:
> On 2/13/23 15:43, Huang, Kai wrote:
> > ( My main concern is "Run after the KVM handler" seems a little bit hacky to me.
> > Logically, it's more reasonable to have the TDX callback _before_ KVM's but not
> > _after_.  If any user (KVM) has done tdx_enable() successfully, the TDX code
> > should give the user a "TDX-runnable" cpu before user (KVM)'s own callback is
> > involved. Anyway as mentioned above, I'll do above as you suggested.)
> 
> I was assuming that the KVM callback is what does VMXON for a given
> logical CPU.  If that were the case, you'd need to do the TDX stuff
> *AFTER* VMXON.
> 
> Am I wrong?
> 
> 

You are right.

What I meant was: because we choose to not support VMXON in the (non-KVM)
kernel, we need/have to put TDX's callback after KVM's.  Otherwise, perhaps a
better way is to put TDX's callback before KVM's.  But maybe it's an arguable
"perhaps", so let's just do TDX's callback after KVM's as you suggested.