linux-kernel - Re: [PATCH v1 3/4] KVM: VMX: Handle the immediate form of MSR instructions

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Message-ID: <9930f714-4ec8-41be-b9ab-44bac38e0bb7@zytor.com>
Date: Thu, 31 Jul 2025 15:10:07 -0700
From: Xin Li <xin@...or.com>
To: Chao Gao <chao.gao@...el.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, pbonzini@...hat.com,
        seanjc@...gle.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com
Subject: Re: [PATCH v1 3/4] KVM: VMX: Handle the immediate form of MSR
 instructions

On 7/31/2025 9:53 AM, Xin Li wrote:
>> The CPUID feature bit also indicates support for the two new VM-exit 
>> reasons.
>> Therefore, KVM needs to reflect EXIT_REASON_MSR_READ/WRITE_IMM VM- 
>> exits to
>> L1 guests in nested cases if KVM claims it supports the new form of MSR
>> instructions.
> 
> Damn, forgot about nested...

The current nested KVM VMX implementation already handles VM exits
caused by the immediate form of MSR instructions, forwarding them to L1
as intended by design.

I just need to add MSR bitmap checks to nested_vmx_exit_handled_msr().

Thanks!
     Xin