KVM: TDX: Handle TDX PV rdmsr/wrmsr hypercall

Morph PV RDMSR/WRMSR hypercall to EXIT_REASON_MSR_{READ,WRITE} and
wire up KVM backend functions.

For complete_emulated_msr() callback, instead of injecting #GP on error,
implement tdx_complete_emulated_msr() to set return code on error.  Also
set return value on MSR read according to the values from kvm x86
registers.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250227012021.1778144-10-binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: yamahata

arch/x86/kvm/vmx/main.c

@@ -235,6 +235,14 @@ static void vt_msr_filter_changed(struct kvm_vcpu *vcpu)
 	vmx_msr_filter_changed(vcpu);
 }
 
+static int vt_complete_emulated_msr(struct kvm_vcpu *vcpu, int err)
+{
+	if (is_td_vcpu(vcpu))
+		return tdx_complete_emulated_msr(vcpu, err);
+
+	return kvm_complete_insn_gp(vcpu, err);
+}
+
 #ifdef CONFIG_KVM_SMM
 static int vt_smi_allowed(struct kvm_vcpu *vcpu, bool for_injection)
 {
@@ -686,7 +694,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.migrate_timers = vmx_migrate_timers,
 
 	.msr_filter_changed = vt_msr_filter_changed,
-	.complete_emulated_msr = kvm_complete_insn_gp,
+	.complete_emulated_msr = vt_complete_emulated_msr,
 
 	.vcpu_deliver_sipi_vector = kvm_vcpu_deliver_sipi_vector,
 

arch/x86/kvm/vmx/tdx.c

@@ -877,6 +877,8 @@ static __always_inline u32 tdcall_to_vmx_exit_reason(struct kvm_vcpu *vcpu)
 	case EXIT_REASON_CPUID:
 	case EXIT_REASON_HLT:
 	case EXIT_REASON_IO_INSTRUCTION:
+	case EXIT_REASON_MSR_READ:
+	case EXIT_REASON_MSR_WRITE:
 		return tdvmcall_leaf(vcpu);
 	case EXIT_REASON_EPT_VIOLATION:
 		return EXIT_REASON_EPT_MISCONFIG;
@@ -1906,6 +1908,20 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
 	return ret;
 }
 
+int tdx_complete_emulated_msr(struct kvm_vcpu *vcpu, int err)
+{
+	if (err) {
+		tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND);
+		return 1;
+	}
+
+	if (vmx_get_exit_reason(vcpu).basic == EXIT_REASON_MSR_READ)
+		tdvmcall_set_return_val(vcpu, kvm_read_edx_eax(vcpu));
+
+	return 1;
+}
+
+
 int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
 {
 	struct vcpu_tdx *tdx = to_tdx(vcpu);
@@ -1971,6 +1987,14 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
 		return tdx_emulate_vmcall(vcpu);
 	case EXIT_REASON_IO_INSTRUCTION:
 		return tdx_emulate_io(vcpu);
+	case EXIT_REASON_MSR_READ:
+		kvm_rcx_write(vcpu, tdx->vp_enter_args.r12);
+		return kvm_emulate_rdmsr(vcpu);
+	case EXIT_REASON_MSR_WRITE:
+		kvm_rcx_write(vcpu, tdx->vp_enter_args.r12);
+		kvm_rax_write(vcpu, tdx->vp_enter_args.r13 & -1u);
+		kvm_rdx_write(vcpu, tdx->vp_enter_args.r13 >> 32);
+		return kvm_emulate_wrmsr(vcpu);
 	case EXIT_REASON_EPT_MISCONFIG:
 		return tdx_emulate_mmio(vcpu);
 	case EXIT_REASON_EPT_VIOLATION:

arch/x86/kvm/vmx/tdx.h

@@ -173,6 +173,7 @@ static __always_inline void td_##lclass##_clearbit##bits(struct vcpu_tdx *tdx,	\
 
 
 bool tdx_interrupt_allowed(struct kvm_vcpu *vcpu);
+int tdx_complete_emulated_msr(struct kvm_vcpu *vcpu, int err);
 
 TDX_BUILD_TDVPS_ACCESSORS(16, VMCS, vmcs);
 TDX_BUILD_TDVPS_ACCESSORS(32, VMCS, vmcs);
@@ -196,6 +197,7 @@ struct vcpu_tdx {
 };
 
 static inline bool tdx_interrupt_allowed(struct kvm_vcpu *vcpu) { return false; }
+static inline int tdx_complete_emulated_msr(struct kvm_vcpu *vcpu, int err) { return 0; }
 
 #endif