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SubjectRe: [RFC PATCH v6 090/104] KVM: TDX: Handle TDX PV CPUID hypercall
On Thu, May 5, 2022 at 11:16 AM <isaku.yamahata@intel.com> wrote:
>
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> Wire up TDX PV CPUID hypercall to the KVM backend function.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
> arch/x86/kvm/vmx/tdx.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 9c712f661a7c..c7cdfee397ec 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -946,12 +946,34 @@ static int tdx_emulate_vmcall(struct kvm_vcpu *vcpu)
> return 1;
> }
>
> +static int tdx_emulate_cpuid(struct kvm_vcpu *vcpu)
> +{
> + u32 eax, ebx, ecx, edx;
> +
> + /* EAX and ECX for cpuid is stored in R12 and R13. */
> + eax = tdvmcall_a0_read(vcpu);
> + ecx = tdvmcall_a1_read(vcpu);
> +
> + kvm_cpuid(vcpu, &eax, &ebx, &ecx, &edx, true);

According to the GHCI spec section 3.6
(TDG.VP.VMCALL<Instruction.CPUID>) we should return
VMCALL_INVALID_OPERAND if an invalid CPUID is requested.

kvm_cpuid already returns false in this case so we should use that
return value to set the tdvmcall return code in case of invalid leaf.
> +
> + tdvmcall_a0_write(vcpu, eax);
> + tdvmcall_a1_write(vcpu, ebx);
> + tdvmcall_a2_write(vcpu, ecx);
> + tdvmcall_a3_write(vcpu, edx);
> +
> + tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_SUCCESS);
> +
> + return 1;
> +}
> +
> static int handle_tdvmcall(struct kvm_vcpu *vcpu)
> {
> if (tdvmcall_exit_type(vcpu))
> return tdx_emulate_vmcall(vcpu);
>
> switch (tdvmcall_leaf(vcpu)) {
> + case EXIT_REASON_CPUID:
> + return tdx_emulate_cpuid(vcpu);
> default:
> break;
> }
> --
> 2.25.1
>

Sagi

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