linux-kernel - RE: [PATCH v2 08/25] KVM: VMX: Initialize VMCS FRED fields

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Date: Fri, 19 Apr 2024 17:02:59 +0000
From: "Li, Xin3" <xin3.li@...el.com>
To: "Gao, Chao" <chao.gao@...el.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, "linux-kselftest@...r.kernel.org"
	<linux-kselftest@...r.kernel.org>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "corbet@....net"
	<corbet@....net>, "tglx@...utronix.de" <tglx@...utronix.de>,
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	"peterz@...radead.org" <peterz@...radead.org>, "Shankar, Ravi V"
	<ravi.v.shankar@...el.com>, "xin@...or.com" <xin@...or.com>
Subject: RE: [PATCH v2 08/25] KVM: VMX: Initialize VMCS FRED fields

> >+#ifdef CONFIG_X86_64
> 
> is this #ifdeffery neccesary?

Yes, otherwise build fails on 32 bit.

> 
> I assume kvm_cpu_cap_has(X86_FEATURE_FRED) is always false
> for !CONFIG_X86_64.
> Looks most of FRED changes in core kernel don't have such #ifdeffery.

Because it's not a compile time false, instead false from runtime.

> 
> >+		/* Per-CPU FRED MSRs */
> 
> Please explain why these six MSRs are updated here and why only they are updated in
> this comment.

The explanation is kind of implicit "per-CPU", I will make it more explicit	

Thanks!
    Xin