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

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Message-ID: <aM3VCPaq8apAJLoW@google.com>
Date: Fri, 19 Sep 2025 15:11:20 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>
Cc: 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>, 
	Chao Gao <chao.gao@...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, 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?

Yes?  My comment there is stating what I did relative to the patch Chao sent.
It's not relative to any existing code.