Add ucall test support for LoongArch, ucall method on LoongArch uses
undefined mmio area. It will cause vCPU exits to hypervisor so that
hypervisor can communicate with vCPU.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
---
 .../selftests/kvm/include/loongarch/ucall.h   | 20 ++++++++++
 .../selftests/kvm/lib/loongarch/ucall.c       | 38 +++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/include/loongarch/ucall.h
 create mode 100644 tools/testing/selftests/kvm/lib/loongarch/ucall.c

diff --git a/tools/testing/selftests/kvm/include/loongarch/ucall.h b/tools/testing/selftests/kvm/include/loongarch/ucall.h
new file mode 100644
index 000000000000..4ec801f37f00
--- /dev/null
+++ b/tools/testing/selftests/kvm/include/loongarch/ucall.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef SELFTEST_KVM_UCALL_H
+#define SELFTEST_KVM_UCALL_H
+
+#include "kvm_util.h"
+
+#define UCALL_EXIT_REASON       KVM_EXIT_MMIO
+
+/*
+ * ucall_exit_mmio_addr holds per-VM values (global data is duplicated by each
+ * VM), it must not be accessed from host code.
+ */
+extern vm_vaddr_t *ucall_exit_mmio_addr;
+
+static inline void ucall_arch_do_ucall(vm_vaddr_t uc)
+{
+	WRITE_ONCE(*ucall_exit_mmio_addr, uc);
+}
+
+#endif
diff --git a/tools/testing/selftests/kvm/lib/loongarch/ucall.c b/tools/testing/selftests/kvm/lib/loongarch/ucall.c
new file mode 100644
index 000000000000..fc6cbb50573f
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/loongarch/ucall.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ucall support. A ucall is a "hypercall to userspace".
+ *
+ */
+#include "kvm_util.h"
+
+/*
+ * ucall_exit_mmio_addr holds per-VM values (global data is duplicated by each
+ * VM), it must not be accessed from host code.
+ */
+vm_vaddr_t *ucall_exit_mmio_addr;
+
+void ucall_arch_init(struct kvm_vm *vm, vm_paddr_t mmio_gpa)
+{
+	vm_vaddr_t mmio_gva = vm_vaddr_unused_gap(vm, vm->page_size, KVM_UTIL_MIN_VADDR);
+
+	virt_map(vm, mmio_gva, mmio_gpa, 1);
+
+	vm->ucall_mmio_addr = mmio_gpa;
+
+	write_guest_global(vm, ucall_exit_mmio_addr, (vm_vaddr_t *)mmio_gva);
+}
+
+void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
+{
+	struct kvm_run *run = vcpu->run;
+
+	if (run->exit_reason == KVM_EXIT_MMIO &&
+	    run->mmio.phys_addr == vcpu->vm->ucall_mmio_addr) {
+		TEST_ASSERT(run->mmio.is_write && run->mmio.len == sizeof(uint64_t),
+			    "Unexpected ucall exit mmio address access");
+
+		return (void *)(*((uint64_t *)run->mmio.data));
+	}
+
+	return NULL;
+}
-- 
2.39.3