KVM: riscv: selftests: Add exception handling support

Add the infrastructure for guest exception handling in riscv selftests.
Customized handlers can be enabled by vm_install_exception_handler(vector)
or vm_install_interrupt_handler().

The code is inspired from that of x86/arm64.

Signed-off-by: Haibo Xu <haibo1.xu@intel.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

1 files changed, 69 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/lib/riscv/processor.c b/tools/testing/selftests/kvm/lib/riscv/processor.c
index 2bb33a8ac03c..87ce44992c87 100644
--- a/tools/testing/selftests/kvm/lib/riscv/processor.c
+++ b/tools/testing/selftests/kvm/lib/riscv/processor.c
@@ -13,6 +13,8 @@
 
 #define DEFAULT_RISCV_GUEST_STACK_VADDR_MIN	0xac0000
 
+static vm_vaddr_t exception_handlers;
+
 static uint64_t page_align(struct kvm_vm *vm, uint64_t v)
 {
 	return (v + vm->page_size) & ~(vm->page_size - 1);
@@ -364,8 +366,75 @@ void vcpu_args_set(struct kvm_vcpu *vcpu, unsigned int num, ...)
 	va_end(ap);
 }
 
+void kvm_exit_unexpected_exception(int vector, int ec)
+{
+	ucall(UCALL_UNHANDLED, 2, vector, ec);
+}
+
 void assert_on_unhandled_exception(struct kvm_vcpu *vcpu)
 {
+	struct ucall uc;
+
+	if (get_ucall(vcpu, &uc) == UCALL_UNHANDLED) {
+		TEST_FAIL("Unexpected exception (vector:0x%lx, ec:0x%lx)",
+			uc.args[0], uc.args[1]);
+	}
+}
+
+struct handlers {
+	exception_handler_fn exception_handlers[NR_VECTORS][NR_EXCEPTIONS];
+};
+
+void route_exception(struct ex_regs *regs)
+{
+	struct handlers *handlers = (struct handlers *)exception_handlers;
+	int vector = 0, ec;
+
+	ec = regs->cause & ~CAUSE_IRQ_FLAG;
+	if (ec >= NR_EXCEPTIONS)
+		goto unexpected_exception;
+
+	/* Use the same handler for all the interrupts */
+	if (regs->cause & CAUSE_IRQ_FLAG) {
+		vector = 1;
+		ec = 0;
+	}
+
+	if (handlers && handlers->exception_handlers[vector][ec])
+		return handlers->exception_handlers[vector][ec](regs);
+
+unexpected_exception:
+	return kvm_exit_unexpected_exception(vector, ec);
+}
+
+void vcpu_init_vector_tables(struct kvm_vcpu *vcpu)
+{
+	extern char exception_vectors;
+
+	vcpu_set_reg(vcpu, RISCV_GENERAL_CSR_REG(stvec), (unsigned long)&exception_vectors);
+}
+
+void vm_init_vector_tables(struct kvm_vm *vm)
+{
+	vm->handlers = __vm_vaddr_alloc(vm, sizeof(struct handlers),
+				   vm->page_size, MEM_REGION_DATA);
+
+	*(vm_vaddr_t *)addr_gva2hva(vm, (vm_vaddr_t)(&exception_handlers)) = vm->handlers;
+}
+
+void vm_install_exception_handler(struct kvm_vm *vm, int vector, exception_handler_fn handler)
+{
+	struct handlers *handlers = addr_gva2hva(vm, vm->handlers);
+
+	assert(vector < NR_EXCEPTIONS);
+	handlers->exception_handlers[0][vector] = handler;
+}
+
+void vm_install_interrupt_handler(struct kvm_vm *vm, exception_handler_fn handler)
+{
+	struct handlers *handlers = addr_gva2hva(vm, vm->handlers);
+
+	handlers->exception_handlers[1][0] = handler;
 }
 
 struct sbiret sbi_ecall(int ext, int fid, unsigned long arg0,