linux-kernel - Re: [RFC PATCH v5 027/104] KVM: TDX: initialize VM with TDX specific parameters

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Date:   Wed, 6 Apr 2022 10:06:16 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Kai Huang <kai.huang@...el.com>, isaku.yamahata@...el.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Jim Mattson <jmattson@...gle.com>,
        erdemaktas@...gle.com, Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 027/104] KVM: TDX: initialize VM with TDX specific
 parameters

On 4/5/2022 9:01 PM, Paolo Bonzini wrote:
> On 3/31/22 06:55, Kai Huang wrote:
>>> +struct kvm_tdx_init_vm {
>>> +    __u32 max_vcpus;
>>> +    __u32 tsc_khz;
>>> +    __u64 attributes;
>>> +    __u64 cpuid;
>> Is it better to append all CPUIDs directly into this structure, 
>> perhaps at end
>> of this structure, to make it more consistent with TD_PARAMS?
>>
>> Also, I think somewhere in commit message or comments we should 
>> explain why
>> CPUIDs are passed here (why existing KVM_SET_CUPID2 is not sufficient).
>>
> 
> Indeed, it would be easier to use the existing cpuid data in struct 
> kvm_vcpu, because right now there is no way to ensure that they are 
> consistent.
> 
> Why is KVM_SET_CPUID2 not enough?  Are there any modifications done by 
> KVM that affect the measurement?

Then we get the situation that KVM_TDX_INIT_VM must be called after 1 
vcpu is created. It seems illogical that it has chance to fail the VM 
scope initialization after 1 vcpu is successfully created.

> Thanks,
> 
> Paolo
>