linux-kernel - Re: [PATCH v14 07/23] x86/virt/tdx: Add skeleton to enable TDX on demand

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Message-ID: <5fca35af-b390-46d1-b5ab-9312fa740599@suse.com>
Date:   Wed, 18 Oct 2023 11:39:14 +0300
From:   Nikolay Borisov <nik.borisov@...e.com>
To:     "Huang, Kai" <kai.huang@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "david@...hat.com" <david@...hat.com>,
        "bagasdotme@...il.com" <bagasdotme@...il.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "imammedo@...hat.com" <imammedo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "Gao, Chao" <chao.gao@...el.com>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "Brown, Len" <len.brown@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v14 07/23] x86/virt/tdx: Add skeleton to enable TDX on
 demand



On 18.10.23 г. 11:29 ч., Huang, Kai wrote:
>   
>>> +/*
>>> + * Do the module global initialization once and return its result.
>>> + * It can be done on any cpu.  It's always called with interrupts
>>> + * disabled.
>>> + */
>>> +static int try_init_module_global(void)
>>> +{
>>
>> Any particular reason why this function is not called from the tdx
>> module's tdx_init? It's global and must be called once when the module
>> is initialised. Subsequently kvm which is supposed to call
>> tdx_cpu_enable() must be sequenced _after_ tdx which shouldn't be that
>> hard, no? This will eliminate the spinlock as well.
>>
> 
> Do you mean early_initcall(tdx_init)?
> 
> Because it requires VMXON being done to do SEAMCALL.  For now only KVM does
> VMXON.
> 

Right, then would it not make more sense too have this code as part of 
the KVM bringup of TDX. In fact by keeping the 2 series separate you 
might be adding complexity. What is the initial motivation to keep those 
patches out of the KVM tdx host series support?