linux-kernel - Re: [PATCH v14 111/113] RFC: KVM: x86, TDX: Add check for setting CPUID

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Message-ID: <0bb55025908cdc4011175603744a36549e235d58.camel@intel.com>
Date:   Wed, 14 Jun 2023 09:43:55 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>
CC:     "Christopherson,, Sean" <seanjc@...gle.com>,
        "Chen, Bo2" <chen.bo@...el.com>, "Shahar, Sagi" <sagis@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "zhi.wang.linux@...il.com" <zhi.wang.linux@...il.com>
Subject: Re: [PATCH v14 111/113] RFC: KVM: x86, TDX: Add check for setting
 CPUID

On Tue, 2023-06-13 at 10:31 -0700, Isaku Yamahata wrote:
> On Tue, Jun 06, 2023 at 11:57:35PM +0000,
> "Huang, Kai" <kai.huang@...el.com> wrote:
> 
> > On Sun, 2023-05-28 at 21:20 -0700, isaku.yamahata@...el.com wrote:
> > > From: Isaku Yamahata <isaku.yamahata@...el.com>
> > > 
> > > Add a hook to setting CPUID for additional consistency check of
> > > KVM_SET_CPUID2.
> > > 
> > > Because intel TDX or AMD SNP has restriction on the value of cpuid.  Some
> > > value can't be changed after boot.  Some can be only set at the VM
> > > creation time and can't be changed later.  Check if the new values are
> > > consistent with the old values.
> > 
> > You might want to use some grammar tool to check against the changelog.
> > 
> > Also, personally I think it's better to briefly mention why we choose this
> > design but not another (e.g., why we just don't make KVM remember all CPUIDs in
> > TDH.MNG.INIT and simply ignores/rejects further KVM_SET_CPUID2).  It would be
> > helpful for the reviewer, or some git blamer in the future.
> > 
> 
> > And why this patch is placed at the very bottom of this series? This logic
> > should belong to TD creation part which should be at a relative earlier position
> > in this series.
> 
> Because this is nice-to-have, not necessary for this patch series to work.  

Is it?  I thought Sean suggested we should to this.

I think you should just include it to this series and place it in a proper
position (or even merge it to some other patch).