RISC-V: KVM: Implement SBI v0.3 SRST extension

The SBI v0.3 specification defines SRST (System Reset) extension which
provides a standard poweroff and reboot interface. This patch implements
SRST extension for the KVM Guest.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/kvm/vcpu_sbi.c

@@ -45,6 +45,7 @@ extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_base;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_time;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_ipi;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_rfence;
+extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_srst;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
 extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;
@@ -55,6 +56,7 @@ static const struct kvm_vcpu_sbi_extension *sbi_ext[] = {
 	&vcpu_sbi_ext_time,
 	&vcpu_sbi_ext_ipi,
 	&vcpu_sbi_ext_rfence,
+	&vcpu_sbi_ext_srst,
 	&vcpu_sbi_ext_hsm,
 	&vcpu_sbi_ext_experimental,
 	&vcpu_sbi_ext_vendor,

arch/riscv/kvm/vcpu_sbi_replace.c

@@ -130,3 +130,47 @@ const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_rfence = {
 	.extid_end = SBI_EXT_RFENCE,
 	.handler = kvm_sbi_ext_rfence_handler,
 };
+
+static int kvm_sbi_ext_srst_handler(struct kvm_vcpu *vcpu,
+				    struct kvm_run *run,
+				    unsigned long *out_val,
+				    struct kvm_cpu_trap *utrap, bool *exit)
+{
+	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
+	unsigned long funcid = cp->a6;
+	u32 reason = cp->a1;
+	u32 type = cp->a0;
+	int ret = 0;
+
+	switch (funcid) {
+	case SBI_EXT_SRST_RESET:
+		switch (type) {
+		case SBI_SRST_RESET_TYPE_SHUTDOWN:
+			kvm_riscv_vcpu_sbi_system_reset(vcpu, run,
+						KVM_SYSTEM_EVENT_SHUTDOWN,
+						reason);
+			*exit = true;
+			break;
+		case SBI_SRST_RESET_TYPE_COLD_REBOOT:
+		case SBI_SRST_RESET_TYPE_WARM_REBOOT:
+			kvm_riscv_vcpu_sbi_system_reset(vcpu, run,
+						KVM_SYSTEM_EVENT_RESET,
+						reason);
+			*exit = true;
+			break;
+		default:
+			ret = -EOPNOTSUPP;
+		}
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+	return ret;
+}
+
+const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_srst = {
+	.extid_start = SBI_EXT_SRST,
+	.extid_end = SBI_EXT_SRST,
+	.handler = kvm_sbi_ext_srst_handler,
+};