RISC-V: KVM: selftests: Add ebreak test support

Initial support for RISC-V KVM ebreak test. Check the exit reason and
the PC when guest debug is enabled. Also to make sure the guest could
handle the ebreak exception without exiting to the VMM when guest debug
is not enabled.

Signed-off-by: Chao Du <duchao@eswincomputing.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20240402062628.5425-4-duchao@eswincomputing.com
Signed-off-by: Anup Patel <anup@brainfault.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/riscv/ebreak_test.c b/tools/testing/selftests/kvm/riscv/ebreak_test.c
new file mode 100644
index 000000000000..823c132069b4
--- /dev/null
+++ b/tools/testing/selftests/kvm/riscv/ebreak_test.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * RISC-V KVM ebreak test.
+ *
+ * Copyright 2024 Beijing ESWIN Computing Technology Co., Ltd.
+ *
+ */
+#include "kvm_util.h"
+
+#define LABEL_ADDRESS(v) ((uint64_t)&(v))
+
+extern unsigned char sw_bp_1, sw_bp_2;
+static uint64_t sw_bp_addr;
+
+static void guest_code(void)
+{
+	asm volatile(
+		".option push\n"
+		".option norvc\n"
+		"sw_bp_1: ebreak\n"
+		"sw_bp_2: ebreak\n"
+		".option pop\n"
+	);
+	GUEST_ASSERT_EQ(READ_ONCE(sw_bp_addr), LABEL_ADDRESS(sw_bp_2));
+
+	GUEST_DONE();
+}
+
+static void guest_breakpoint_handler(struct ex_regs *regs)
+{
+	WRITE_ONCE(sw_bp_addr, regs->epc);
+	regs->epc += 4;
+}
+
+int main(void)
+{
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+	uint64_t pc;
+	struct kvm_guest_debug debug = {
+		.control = KVM_GUESTDBG_ENABLE,
+	};
+
+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_SET_GUEST_DEBUG));
+
+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+
+	vm_init_vector_tables(vm);
+	vcpu_init_vector_tables(vcpu);
+	vm_install_exception_handler(vm, EXC_BREAKPOINT,
+					guest_breakpoint_handler);
+
+	/*
+	 * Enable the guest debug.
+	 * ebreak should exit to the VMM with KVM_EXIT_DEBUG reason.
+	 */
+	vcpu_guest_debug_set(vcpu, &debug);
+	vcpu_run(vcpu);
+
+	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_DEBUG);
+
+	vcpu_get_reg(vcpu, RISCV_CORE_REG(regs.pc), &pc);
+	TEST_ASSERT_EQ(pc, LABEL_ADDRESS(sw_bp_1));
+
+	/* skip sw_bp_1 */
+	vcpu_set_reg(vcpu, RISCV_CORE_REG(regs.pc), pc + 4);
+
+	/*
+	 * Disable all debug controls.
+	 * Guest should handle the ebreak without exiting to the VMM.
+	 */
+	memset(&debug, 0, sizeof(debug));
+	vcpu_guest_debug_set(vcpu, &debug);
+
+	vcpu_run(vcpu);
+
+	TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);
+
+	kvm_vm_free(vm);
+
+	return 0;
+}