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Date: Mon, 25 Mar 2024 21:43:31 +1300
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Subject: Re: [PATCH v19 037/130] KVM: TDX: Make KVM_CAP_MAX_VCPUS backend
 specific
To: "Yamahata, Isaku" <isaku.yamahata@intel.com>
CC: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>, Paolo Bonzini
	<pbonzini@redhat.com>, "Aktas, Erdem" <erdemaktas@google.com>, "Sean
 Christopherson" <seanjc@google.com>, Sagi Shahar <sagis@google.com>, "Chen,
 Bo2" <chen.bo@intel.com>, "Yuan, Hang" <hang.yuan@intel.com>, "Zhang, Tina"
	<tina.zhang@intel.com>, "isaku.yamahata@linux.intel.com"
	<isaku.yamahata@linux.intel.com>
References: <cover.1708933498.git.isaku.yamahata@intel.com>
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From: "Huang, Kai" <kai.huang@intel.com>
In-Reply-To: <20240323011335.GC2357401@ls.amr.corp.intel.com>
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>> Currently, the KVM x86 always reports KVM_MAX_VCPUS for all VMs but doesn't
>> allow to enable KVM_CAP_MAX_VCPUS to configure the number of maximum vcpus
>                                                       maximum number of vcpus
>> on VM-basis.
>>
>> Add "per-VM maximum vcpus" to KVM x86/TDX to accommodate TDX's needs.
>>
>> The userspace-configured value then can be verified when KVM is actually
>                                               used
>> creating the TDX guest.
>> "

I think we still have two options regarding to how 'max_vcpus' is 
handled in ioctl() to do TDH.MNG.INIT:

1) Just use the 'max_vcpus' done in KVM_ENABLE_CAP(KVM_CAP_MAX_VCPUS),
2) Still pass the 'max_vcpus' as input, but KVM verifies it against the 
value that is saved in KVM_ENABLE_CAP(KVM_CAP_MAX_VCPUS).

2) seems unnecessary, so I don't have objection to use 1).  But it seems 
we could still mention it in the changelog in that patch?