[PATCH 04/18] KVM: TDX: Handle TDX PV CPUID hypercall

[Binbin Wu <binbin.wu@linux.intel.com>]

From: Isaku Yamahata <isaku.yamahata@intel.com>

Handle TDX PV CPUID hypercall for the CPUIDs virtualized by VMM
according to TDX Guest Host Communication Interface (GHCI).

For TDX, most CPUID leaf/sub-leaf combinations are virtualized by
the TDX module while some trigger #VE.  On #VE, TDX guest can issue
TDG.VP.VMCALL<INSTRUCTION.CPUID> (same value as EXIT_REASON_CPUID)
to request VMM to emulate CPUID operation.

Wire up TDX PV CPUID hypercall to the KVM backend function.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
[binbin: rewrite changelog]
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
---
TDX "the rest" breakout:
- Rewrite changelog.
- Use TDVMCALL_STATUS prefix for TDX call status codes (Binbin)
---
 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 96b05e445837..62dbb47ead21 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1274,6 +1274,26 @@ static int tdx_report_fatal_error(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+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, false);
+
+	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, TDVMCALL_STATUS_SUCCESS);
+
+	return 1;
+}
+
 static int tdx_complete_pio_out(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.pio.count = 0;
@@ -1455,6 +1475,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu)
 		return tdx_map_gpa(vcpu);
 	case TDVMCALL_REPORT_FATAL_ERROR:
 		return tdx_report_fatal_error(vcpu);
+	case EXIT_REASON_CPUID:
+		return tdx_emulate_cpuid(vcpu);
 	case EXIT_REASON_IO_INSTRUCTION:
 		return tdx_emulate_io(vcpu);
 	case EXIT_REASON_EPT_VIOLATION:
-- 
2.46.0