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Date:   Thu, 7 Apr 2022 20:33:57 -0700
From:   Isaku Yamahata <isaku.yamahata@gmail.com>
To:     Kai Huang <kai.huang@intel.com>
Cc:     Xiaoyao Li <xiaoyao.li@intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>, isaku.yamahata@intel.com,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        isaku.yamahata@gmail.com, Jim Mattson <jmattson@google.com>,
        erdemaktas@google.com, Connor Kuehl <ckuehl@redhat.com>,
        Sean Christopherson <seanjc@google.com>
Subject: Re: [RFC PATCH v5 027/104] KVM: TDX: initialize VM with TDX specific
 parameters
Message-ID: <20220408033357.GF2864606@ls.amr.corp.intel.com>
References: <cover.1646422845.git.isaku.yamahata@intel.com>
 <c3b37cf5c83f92be0e153075d81a80729bf1031e.1646422845.git.isaku.yamahata@intel.com>
 <e392b53a-fbaa-4724-07f4-171424144f70@redhat.com>
 <a1052ec0-4ea6-d5db-a729-deec08712683@intel.com>
 <34d773c8d32c8d38033aae7e0fee572d757e242c.camel@intel.com>
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On Thu, Apr 07, 2022 at 01:51:38PM +1200,
Kai Huang <kai.huang@intel.com> wrote:

> On Thu, 2022-04-07 at 09:29 +0800, Xiaoyao Li wrote:
> > On 4/5/2022 8:58 PM, Paolo Bonzini wrote:
> > > On 3/4/22 20:48, isaku.yamahata@intel.com wrote:
> > > > +    td_params->attributes = init_vm->attributes;
> > > > +    if (td_params->attributes & TDX_TD_ATTRIBUTE_PERFMON) {
> > > > +        pr_warn("TD doesn't support perfmon. KVM needs to save/restore "
> > > > +            "host perf registers properly.\n");
> > > > +        return -EOPNOTSUPP;
> > > > +    }
> > > 
> > > Why does KVM have to hardcode this (and LBR/AMX below)?  Is the level of 
> > > hardware support available from tdx_caps, for example through the CPUID 
> > > configs (0xA for this one, 0xD for LBR and AMX)?
> > 
> > It's wrong code. PMU is allowed.
> > 
> > AMX and LBR are disallowed because and the time we wrote the codes they 
> > are not supported by KVM. Now AMX should be allowed, but (arch-)LBR 
> > should be still blocked until KVM merges arch-LBR support.
> 
> I think Isaku's idea is we don't support them in the first submission?
> 
> If so as I suggested, we should add a TODO in comment..

Sure, will add a TODO comment.

-- 
Isaku Yamahata <isaku.yamahata@gmail.com>