Re: [PATCH v10 098/108] KVM: TDX: Implement callbacks for MSR operations for TDX

Isaku Yamahata
2022-12-16T01:29:59Z

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>