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    SubjectRe: [PATCH v19 111/130] KVM: TDX: Implement callbacks for MSR operations for TDX
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    On 2/26/2024 4:26 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.
    >
    > 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 virtualize the MSRs.
    >
    > 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 case
    > Guest TD would issue TDG.VP.VMCALL<INSTRUCTION.{WRMSR,RDMSR> and
    > VMM handles the MSR hypercall. The value set by KVM_SET_MSR_INDEX_LIST
    > is used.
    >
    > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
    > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
    > ---
    [...]
    > +
    > +bool tdx_has_emulated_msr(u32 index, bool write)
    > +{
    > + switch (index) {
    > + case MSR_IA32_UCODE_REV:
    > + case MSR_IA32_ARCH_CAPABILITIES:
    > + case MSR_IA32_POWER_CTL:
    > + case MSR_IA32_CR_PAT:
    > + case MSR_IA32_TSC_DEADLINE:
    > + case MSR_IA32_MISC_ENABLE:
    > + case MSR_PLATFORM_INFO:
    > + case MSR_MISC_FEATURES_ENABLES:
    > + case MSR_IA32_MCG_CAP:
    > + case MSR_IA32_MCG_STATUS:
    It not about this patch directly.

    Intel SDM says:
    "An attempt to write to IA32_MCG_STATUS with any value other than 0
    would result in #GP".

    But in set_msr_mce(), IA32_MCG_STATUS is set without any check.
    Should it be checked against 0 if it is not host_initiated?



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