[PATCH v1 3/4] selftests: kvm: Add ucall tests for LoongArch KVM

[Tianrui Zhao]

Add ucall tests for LoongArch KVM, it means that VM use hypercall
to return to userspace and handle the mmio exception.

Based-on: <20230720062813.4126751-1-zhaotianrui@xxxxxxxxxxx>
Signed-off-by: Tianrui Zhao <zhaotianrui@xxxxxxxxxxx>
---
 .../selftests/kvm/lib/loongarch/ucall.c       | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/lib/loongarch/ucall.c

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..b32f7c7f6548
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/loongarch/ucall.c
@@ -0,0 +1,44 @@
+// 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.
+ */
+static 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_do_ucall(vm_vaddr_t uc)
+{
+
+	WRITE_ONCE(*ucall_exit_mmio_addr, uc);
+}
+
+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;
+}
-- 
2.39.1