linux-kernel - Re: [PATCH v15 14/41] KVM: VMX: Emulate read and write to CET MSRs

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Message-ID: <aMkWT/8cBVwi2mfN@intel.com>
Date: Tue, 16 Sep 2025 15:48:31 +0800
From: Chao Gao <chao.gao@...el.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>
CC: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
	<pbonzini@...hat.com>, <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Tom Lendacky <thomas.lendacky@....com>, Mathias Krause
	<minipli@...ecurity.net>, John Allen <john.allen@....com>, Rick Edgecombe
	<rick.p.edgecombe@...el.com>, Maxim Levitsky <mlevitsk@...hat.com>, "Zhang Yi
 Z" <yi.z.zhang@...ux.intel.com>
Subject: Re: [PATCH v15 14/41] KVM: VMX: Emulate read and write to CET MSRs

On Tue, Sep 16, 2025 at 03:07:06PM +0800, Xiaoyao Li wrote:
>On 9/13/2025 7:22 AM, Sean Christopherson wrote:
>> From: Yang Weijiang <weijiang.yang@...el.com>
>> 
>> Add emulation interface for CET MSR access. The emulation code is split
>> into common part and vendor specific part. The former does common checks
>> for MSRs, e.g., accessibility, data validity etc., then passes operation
>> to either XSAVE-managed MSRs via the helpers or CET VMCS fields.
>> 
>> SSP can only be read via RDSSP. Writing even requires destructive and
>> potentially faulting operations such as SAVEPREVSSP/RSTORSSP or
>> SETSSBSY/CLRSSBSY. Let the host use a pseudo-MSR that is just a wrapper
>> for the GUEST_SSP field of the VMCS.
>> 
>> Suggested-by: Sean Christopherson <seanjc@...gle.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
>> Tested-by: Mathias Krause <minipli@...ecurity.net>
>> Tested-by: John Allen <john.allen@....com>
>> Tested-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
>> Signed-off-by: Chao Gao <chao.gao@...el.com>
>> [sean: drop call to kvm_set_xstate_msr() for S_CET, consolidate code]
>
>Is the change/update of "drop call to kvm_set_xstate_msr() for S_CET" true
>for this patch?

v14 has that call, but it is incorrect. So Sean dropped it. See v14:

https://lore.kernel.org/kvm/20250909093953.202028-12-chao.gao@intel.com/

>
>> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
>
>Reviewed-by: Xiaoyao Li <xiaoyao.li@...el.com>