linux-kernel - Re: [PATCH v3 21/27] KVM: VMX: Invoke vmx_set_cpu

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Message-ID: <edcdad12-bbb7-46b9-8914-9bbb36b44597@zytor.com>
Date: Fri, 25 Oct 2024 00:34:24 -0700
From: Xin Li <xin@...or.com>
To: Chao Gao <chao.gao@...el.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, seanjc@...gle.com, pbonzini@...hat.com,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, peterz@...radead.org, andrew.cooper3@...rix.com
Subject: Re: [PATCH v3 21/27] KVM: VMX: Invoke vmx_set_cpu_caps() before
 nested setup

On 10/24/2024 12:49 AM, Chao Gao wrote:
> On Mon, Sep 30, 2024 at 10:01:04PM -0700, Xin Li (Intel) wrote:
>> From: Xin Li <xin3.li@...el.com>
>>
>> Set VMX CPU capabilities before initializing nested instead of after,
>> as it needs to check VMX CPU capabilities to setup the VMX basic MSR
>> for nested.
> 
> Which VMX CPU capabilities are needed? after reading patch 25, I still
> don't get that.

Sigh, in v2 I had 'if (kvm_cpu_cap_has(X86_FEATURE_FRED))' in
nested_vmx_setup_basic(), which is changed to 'if (cpu_has_vmx_fred())'
in v3.  So the reason for the change is gone.  But I think logically
the change is still needed; nested setup should be after VMX setup.