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

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Message-Id: <88469A8C-CC32-449B-8255-239CAAD6DB91@zytor.com>
Date: Thu, 22 Jan 2026 08:52:53 -0800
From: Xin Li <xin@...or.com>
To: Chao Gao <chao.gao@...el.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


>>>> + 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?
> 

Hmm, this caught me.  Yes, I need to do the same to other FRED MSRs.