KVM: LoongArch: selftests: Add exception handler register interface

Add interrupt and exception handler register interface. When exception
happens, execute registered exception handler if exists, else report an
error.

Signed-off-by: Bibo Mao <[e-mail]>
Signed-off-by: Huacai Chen <[e-mail]>

tools/testing/selftests/kvm/include/loongarch/processor.h

···
 #define LOONGARCH_CSR_EUEN		0x2
 #define LOONGARCH_CSR_ECFG		0x4
 #define LOONGARCH_CSR_ESTAT		0x5  /* Exception status */
+#define  CSR_ESTAT_EXC_SHIFT		16
+#define  CSR_ESTAT_EXC_WIDTH		6
+#define  CSR_ESTAT_EXC			(0x3f << CSR_ESTAT_EXC_SHIFT)
+#define    EXCCODE_INT			0    /* Interrupt */
+#define      INT_TI			11   /* Timer interrupt*/
 #define LOONGARCH_CSR_ERA		0x6  /* ERA */
 #define LOONGARCH_CSR_BADV		0x7  /* Bad virtual address */
 #define LOONGARCH_CSR_EENTRY		0xc
···
 #define BADV_OFFSET_EXREGS		offsetof(struct ex_regs, badv)
 #define PRMD_OFFSET_EXREGS		offsetof(struct ex_regs, prmd)
 #define EXREGS_SIZE			sizeof(struct ex_regs)
+
+#define VECTOR_NUM			64
+
+typedef void(*handler_fn)(struct ex_regs *);
+
+struct handlers {
+	handler_fn exception_handlers[VECTOR_NUM];
+};
+
+void vm_init_descriptor_tables(struct kvm_vm *vm);
+void vm_install_exception_handler(struct kvm_vm *vm, int vector, handler_fn handler);
 
 static inline void cpu_relax(void)
 {

tools/testing/selftests/kvm/lib/loongarch/processor.c

···
 #define LOONGARCH_GUEST_STACK_VADDR_MIN		0x200000
 
 static vm_paddr_t invalid_pgtable[4];
+static vm_vaddr_t exception_handlers;
 
 static uint64_t virt_pte_index(struct kvm_vm *vm, vm_vaddr_t gva, int level)
 {
···
 
 void route_exception(struct ex_regs *regs)
 {
+	int vector;
 	unsigned long pc, estat, badv;
+	struct handlers *handlers;
+
+	handlers = (struct handlers *)exception_handlers;
+	vector = (regs->estat & CSR_ESTAT_EXC) >> CSR_ESTAT_EXC_SHIFT;
+	if (handlers && handlers->exception_handlers[vector])
+		return handlers->exception_handlers[vector](regs);
 
 	pc = regs->pc;
 	badv  = regs->badv;
 	estat = regs->estat;
 	ucall(UCALL_UNHANDLED, 3, pc, estat, badv);
 	while (1) ;
+}
+
+void vm_init_descriptor_tables(struct kvm_vm *vm)
+{
+	void *addr;
+
+	vm->handlers = __vm_vaddr_alloc(vm, sizeof(struct handlers),
+			LOONGARCH_GUEST_STACK_VADDR_MIN, MEM_REGION_DATA);
+
+	addr = addr_gva2hva(vm, vm->handlers);
+	memset(addr, 0, vm->page_size);
+	exception_handlers = vm->handlers;
+	sync_global_to_guest(vm, exception_handlers);
+}
+
+void vm_install_exception_handler(struct kvm_vm *vm, int vector, handler_fn handler)
+{
+	struct handlers *handlers = addr_gva2hva(vm, vm->handlers);
+
+	assert(vector < VECTOR_NUM);
+	handlers->exception_handlers[vector] = handler;
 }
 
 uint32_t guest_get_vcpuid(void)