KVM: SVM: Support string IO operations for an SEV-ES guest

For an SEV-ES guest, string-based port IO is performed to a shared
(un-encrypted) page so that both the hypervisor and guest can read or
write to it and each see the contents.

For string-based port IO operations, invoke SEV-ES specific routines that
can complete the operation using common KVM port IO support.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <9d61daf0ffda496703717218f415cdc8fd487100.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -614,6 +614,7 @@ struct kvm_vcpu_arch {
 
 	struct kvm_pio_request pio;
 	void *pio_data;
+	void *guest_ins_data;
 
 	u8 event_exit_inst_len;
 

arch/x86/kvm/svm/sev.c

@@ -1406,9 +1406,14 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 	case SVM_EXIT_INVD:
 		break;
 	case SVM_EXIT_IOIO:
+		if (ghcb_get_sw_exit_info_1(ghcb) & SVM_IOIO_STR_MASK) {
+			if (!ghcb_sw_scratch_is_valid(ghcb))
+				goto vmgexit_err;
+		} else {
 			if (!(ghcb_get_sw_exit_info_1(ghcb) & SVM_IOIO_TYPE_MASK))
 				if (!ghcb_rax_is_valid(ghcb))
 					goto vmgexit_err;
+		}
 		break;
 	case SVM_EXIT_MSR:
 		if (!ghcb_rcx_is_valid(ghcb))
@@ -1776,3 +1781,12 @@ int sev_handle_vmgexit(struct vcpu_svm *svm)
 
 	return ret;
 }
+
+int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in)
+{
+	if (!setup_vmgexit_scratch(svm, in, svm->vmcb->control.exit_info_2))
+		return -EINVAL;
+
+	return kvm_sev_es_string_io(&svm->vcpu, size, port,
+				    svm->ghcb_sa, svm->ghcb_sa_len, in);
+}

arch/x86/kvm/svm/svm.c

@@ -2038,11 +2038,16 @@ static int io_interception(struct vcpu_svm *svm)
 	++svm->vcpu.stat.io_exits;
 	string = (io_info & SVM_IOIO_STR_MASK) != 0;
 	in = (io_info & SVM_IOIO_TYPE_MASK) != 0;
-	if (string)
-		return kvm_emulate_instruction(vcpu, 0);
-
 	port = io_info >> 16;
 	size = (io_info & SVM_IOIO_SIZE_MASK) >> SVM_IOIO_SIZE_SHIFT;
+
+	if (string) {
+		if (sev_es_guest(vcpu->kvm))
+			return sev_es_string_io(svm, size, port, in);
+		else
+			return kvm_emulate_instruction(vcpu, 0);
+	}
+
 	svm->next_rip = svm->vmcb->control.exit_info_2;
 
 	return kvm_fast_pio(&svm->vcpu, size, port, in);

arch/x86/kvm/svm/svm.h

@@ -573,5 +573,6 @@ void __init sev_hardware_setup(void);
 void sev_hardware_teardown(void);
 void sev_free_vcpu(struct kvm_vcpu *vcpu);
 int sev_handle_vmgexit(struct vcpu_svm *svm);
+int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
 
 #endif

arch/x86/kvm/x86.c

@@ -10783,6 +10783,10 @@ int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu)
 
 unsigned long kvm_get_linear_rip(struct kvm_vcpu *vcpu)
 {
+	/* Can't read the RIP when guest state is protected, just return 0 */
+	if (vcpu->arch.guest_state_protected)
+		return 0;
+
 	if (is_64_bit_mode(vcpu))
 		return kvm_rip_read(vcpu);
 	return (u32)(get_segment_base(vcpu, VCPU_SREG_CS) +
@@ -11415,6 +11419,56 @@ int kvm_sev_es_mmio_read(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned int bytes,
 }
 EXPORT_SYMBOL_GPL(kvm_sev_es_mmio_read);
 
+static int complete_sev_es_emulated_ins(struct kvm_vcpu *vcpu)
+{
+	memcpy(vcpu->arch.guest_ins_data, vcpu->arch.pio_data,
+	       vcpu->arch.pio.count * vcpu->arch.pio.size);
+	vcpu->arch.pio.count = 0;
+
+	return 1;
+}
+
+static int kvm_sev_es_outs(struct kvm_vcpu *vcpu, unsigned int size,
+			   unsigned int port, void *data,  unsigned int count)
+{
+	int ret;
+
+	ret = emulator_pio_out_emulated(vcpu->arch.emulate_ctxt, size, port,
+					data, count);
+	if (ret)
+		return ret;
+
+	vcpu->arch.pio.count = 0;
+
+	return 0;
+}
+
+static int kvm_sev_es_ins(struct kvm_vcpu *vcpu, unsigned int size,
+			  unsigned int port, void *data, unsigned int count)
+{
+	int ret;
+
+	ret = emulator_pio_in_emulated(vcpu->arch.emulate_ctxt, size, port,
+				       data, count);
+	if (ret) {
+		vcpu->arch.pio.count = 0;
+	} else {
+		vcpu->arch.guest_ins_data = data;
+		vcpu->arch.complete_userspace_io = complete_sev_es_emulated_ins;
+	}
+
+	return 0;
+}
+
+int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
+			 unsigned int port, void *data,  unsigned int count,
+			 int in)
+{
+	return in ? kvm_sev_es_ins(vcpu, size, port, data, count)
+		  : kvm_sev_es_outs(vcpu, size, port, data, count);
+}
+EXPORT_SYMBOL_GPL(kvm_sev_es_string_io);
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);

arch/x86/kvm/x86.h

@@ -431,5 +431,8 @@ int kvm_sev_es_mmio_write(struct kvm_vcpu *vcpu, gpa_t src, unsigned int bytes,
 			  void *dst);
 int kvm_sev_es_mmio_read(struct kvm_vcpu *vcpu, gpa_t src, unsigned int bytes,
 			 void *dst);
+int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
+			 unsigned int port, void *data,  unsigned int count,
+			 int in);
 
 #endif