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Date:   Thu, 15 Dec 2022 17:29:51 -0800
From:   Isaku Yamahata <isaku.yamahata@gmail.com>
To:     Binbin Wu <binbin.wu@linux.intel.com>
Cc:     isaku.yamahata@intel.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com,
        Paolo Bonzini <pbonzini@redhat.com>, erdemaktas@google.com,
        Sean Christopherson <seanjc@google.com>,
        Sagi Shahar <sagis@google.com>,
        David Matlack <dmatlack@google.com>
Subject: Re: [PATCH v10 098/108] KVM: TDX: Implement callbacks for MSR
 operations for TDX
Message-ID: <20221216012951.GB527635@ls.amr.corp.intel.com>
References: <cover.1667110240.git.isaku.yamahata@intel.com>
 <1cacbda18e3c7dcccd92a7390b0ca7f4ba073f85.1667110240.git.isaku.yamahata@intel.com>
 <a9832926-8353-fd47-45aa-a6a5b85183e3@linux.intel.com>
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On Wed, Nov 23, 2022 at 10:25:11PM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

> 
> On 10/30/2022 2:23 PM, isaku.yamahata@intel.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@intel.com>
> > 
> > Implements set_msr/get_msr/has_emulated_msr methods for TDX to handle
> > hypercall from guest TD for paravirtualized rdmsr and wrmsr.  The TDX
> > module virtualizes MSRs.  For some MSRs, it injects #VE to the guest TD
> > upon RDMSR or WRMSR.  The exact list of such MSRs are defined in the spec.
> 
> How does KVM handle the case that the userland wants to get the TD MSR list?
> 
> KVM_GET_MSR_INDEX_LIST will return the global KVM MSR list, which is
> different from the TD version.

Do you mean user space VMM (e.g. qemu) by "the userland"?
There are three classes of MSRs virtualization.
- non-configurable: TDX module directly virtualizes it. VMM can't configure.
  the value set by KVM_SET_MSR_INDEX_LIST is ignored.
- configurable: TDX module directly virtualizes it. VMM can configure at the
  VM creation time.
  the value set by KVM_SET_MSR_INDEX_LIST is used.
- #VE
  VMM handles the MSR hypercall by guest TD issues. The value set by
  KVM_SET_MSR_INDEX_LIST is used.


> > Upon #VE, the guest TD may execute hypercalls,
> > TDG.VP.VMCALL<INSTRUCTION.RDMSR> and TDG.VP.VMCALL<INSTRUCTION.WRMSR>,
> > which are defined in GHCI (Guest-Host Communication Interface) so that the
> > host VMM (e.g. KVM) can virtualizes
> can virtualize

Yes, will fix.
-- 
Isaku Yamahata <isaku.yamahata@gmail.com>