linux-kernel - Re: [PATCH v12 12/23] KVM: selftests: Add helper to initialize TDX VM

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Message-ID: <fc4360cd-ac5a-476e-8561-f6e3e990bd09@linux.intel.com>
Date: Thu, 30 Oct 2025 09:25:39 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sagi Shahar <sagis@...gle.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
 Shuah Khan <shuah@...nel.org>, Sean Christopherson <seanjc@...gle.com>,
 Ackerley Tng <ackerleytng@...gle.com>, Ryan Afranji <afranji@...gle.com>,
 Andrew Jones <ajones@...tanamicro.com>,
 Isaku Yamahata <isaku.yamahata@...el.com>,
 Erdem Aktas <erdemaktas@...gle.com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Roger Wang <runanwang@...gle.com>, Oliver Upton <oliver.upton@...ux.dev>,
 "Pratik R. Sampat" <pratikrajesh.sampat@....com>,
 Reinette Chatre <reinette.chatre@...el.com>, Ira Weiny
 <ira.weiny@...el.com>, Chao Gao <chao.gao@...el.com>,
 Chenyi Qiang <chenyi.qiang@...el.com>
Subject: Re: [PATCH v12 12/23] KVM: selftests: Add helper to initialize TDX VM

On 10/29/2025 5:20 AM, Sagi Shahar wrote:
> KVM_TDX_INIT_VM needs to be called after KVM_CREATE_VM and before
> creating any VCPUs, thus before KVM_SET_CPUID2. KVM_TDX_INIT_VM accepts
> the CPUID values directly.
This sentence seems not accurate.
KVM_TDX_INIT_VM, i.e. the seamcall TDH.MNG.INIT, allows only directly
configurable CPUID bits to be 1.

>
> Since KVM_GET_CPUID2 can't be used at this point,

I don't think this is relevant.

As mentioned above, only directly configurable CPUID bits can be 1, so the
CPUIDs input for KVM_TDX_INIT_VM should be filtered against the supported
directly configurable CPUID bits.

>   calculate the CPUID
> values manually by using kvm_get_supported_cpuid() and filter the
> returned CPUIDs against the supported CPUID values read from the TDX

supported CPUID -> supported configurable CPUID

> module.
>
>
[...]