linux-kernel - Re: [PATCH v9 19/22] KVM: nVMX: Handle FRED VMCS fields in nested VMX context

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Message-ID: <aXAhf+ueMAOkiZrf@intel.com>
Date: Wed, 21 Jan 2026 08:44:47 +0800
From: Chao Gao <chao.gao@...el.com>
To: Xin Li <xin@...or.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <pbonzini@...hat.com>, <seanjc@...gle.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>,
	<hch@...radead.org>, <sohil.mehta@...el.com>
Subject: Re: [PATCH v9 19/22] KVM: nVMX: Handle FRED VMCS fields in nested
 VMX context

On Mon, Jan 19, 2026 at 10:30:01PM -0800, Xin Li wrote:
>
>
>> On Dec 1, 2025, at 10:32 PM, Chao Gao <chao.gao@...el.com> wrote:
>> 
>>> +
>>> + nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
>>> +  MSR_IA32_FRED_RSP0, MSR_TYPE_RW);
>> 
>> Why is only this specific MSR handled? What about other FRED MSRs?
>
>Peter just gave a good explanation:
>
>https://lore.kernel.org/lkml/f0768546-a767-4d74-956e-b40128272a09@zytor.com/

Do you need to set up vmcs02's MSR bitmap for other FRED MSRs?

Other FRED MSRs are passed through to L1 guests in patch 8. Is there any
concern about passing through them to L2 guests?