KVM: arm64: selftests: Add basic SError injection test

Add tests for SError injection considering KVM is more directly involved
in delivery:

- Pending SErrors are taken at the first CSE after SErrors are unmasked

- Pending SErrors aren't taken and remain pending if SErrors are masked

- Unmasked SErrors are taken immediately when injected (implementation
detail)

Reviewed-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Oliver Upton <[e-mail]>

tools/testing/selftests/kvm/Makefile.kvm

···
 TEST_GEN_PROGS_arm64 += arm64/debug-exceptions
 TEST_GEN_PROGS_arm64 += arm64/host_sve
 TEST_GEN_PROGS_arm64 += arm64/hypercalls
-TEST_GEN_PROGS_arm64 += arm64/mmio_abort
+TEST_GEN_PROGS_arm64 += arm64/external_aborts
 TEST_GEN_PROGS_arm64 += arm64/page_fault_test
 TEST_GEN_PROGS_arm64 += arm64/psci_test
 TEST_GEN_PROGS_arm64 += arm64/set_id_regs

tools/testing/selftests/kvm/arm64/mmio_abort.c tools/testing/selftests/kvm/arm64/external_aborts.c

···
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * mmio_abort - Tests for userspace MMIO abort injection
+ * external_abort - Tests for userspace external abort injection
  *
  * Copyright (c) 2024 Google LLC
  */
···
 	return vm;
 }
 
-static void vcpu_inject_extabt(struct kvm_vcpu *vcpu)
+static void vcpu_inject_sea(struct kvm_vcpu *vcpu)
 {
 	struct kvm_vcpu_events events = {};
 
···
 	vcpu_events_set(vcpu, &events);
 }
 
-static void vcpu_run_expect_done(struct kvm_vcpu *vcpu)
+static void vcpu_inject_serror(struct kvm_vcpu *vcpu)
+{
+	struct kvm_vcpu_events events = {};
+
+	events.exception.serror_pending = true;
+	vcpu_events_set(vcpu, &events);
+}
+
+static void __vcpu_run_expect(struct kvm_vcpu *vcpu, unsigned int cmd)
 {
 	struct ucall uc;
 
···
 	case UCALL_ABORT:
 		REPORT_GUEST_ASSERT(uc);
 		break;
-	case UCALL_DONE:
-		break;
 	default:
+		if (uc.cmd == cmd)
+			return;
+
 		TEST_FAIL("Unexpected ucall: %lu", uc.cmd);
 	}
+}
+
+static void vcpu_run_expect_done(struct kvm_vcpu *vcpu)
+{
+	__vcpu_run_expect(vcpu, UCALL_DONE);
+}
+
+static void vcpu_run_expect_sync(struct kvm_vcpu *vcpu)
+{
+	__vcpu_run_expect(vcpu, UCALL_SYNC);
 }
 
 extern char test_mmio_abort_insn;
···
 	TEST_ASSERT_EQ(run->mmio.len, sizeof(unsigned long));
 	TEST_ASSERT(!run->mmio.is_write, "Expected MMIO read");
 
-	vcpu_inject_extabt(vcpu);
+	vcpu_inject_sea(vcpu);
 	vcpu_run_expect_done(vcpu);
 	kvm_vm_free(vm);
 }
···
 	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_ARM_NISV);
 	TEST_ASSERT_EQ(run->arm_nisv.fault_ipa, MMIO_ADDR);
 
-	vcpu_inject_extabt(vcpu);
+	vcpu_inject_sea(vcpu);
+	vcpu_run_expect_done(vcpu);
+	kvm_vm_free(vm);
+}
+
+static void unexpected_serror_handler(struct ex_regs *regs)
+{
+	GUEST_FAIL("Took unexpected SError exception");
+}
+
+static void test_serror_masked_guest(void)
+{
+	GUEST_ASSERT(read_sysreg(isr_el1) & ISR_EL1_A);
+
+	isb();
+
+	GUEST_DONE();
+}
+
+static void test_serror_masked(void)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm = vm_create_with_dabt_handler(&vcpu, test_serror_masked_guest,
+							unexpected_dabt_handler);
+
+	vm_install_exception_handler(vm, VECTOR_ERROR_CURRENT, unexpected_serror_handler);
+
+	vcpu_inject_serror(vcpu);
+	vcpu_run_expect_done(vcpu);
+	kvm_vm_free(vm);
+}
+
+static void expect_serror_handler(struct ex_regs *regs)
+{
+	GUEST_DONE();
+}
+
+static void test_serror_guest(void)
+{
+	GUEST_ASSERT(read_sysreg(isr_el1) & ISR_EL1_A);
+
+	local_serror_enable();
+	isb();
+	local_serror_disable();
+
+	GUEST_FAIL("Should've taken pending SError exception");
+}
+
+static void test_serror(void)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm = vm_create_with_dabt_handler(&vcpu, test_serror_guest,
+							unexpected_dabt_handler);
+
+	vm_install_exception_handler(vm, VECTOR_ERROR_CURRENT, expect_serror_handler);
+
+	vcpu_inject_serror(vcpu);
+	vcpu_run_expect_done(vcpu);
+	kvm_vm_free(vm);
+}
+
+static void test_serror_emulated_guest(void)
+{
+	GUEST_ASSERT(!(read_sysreg(isr_el1) & ISR_EL1_A));
+
+	local_serror_enable();
+	GUEST_SYNC(0);
+	local_serror_disable();
+
+	GUEST_FAIL("Should've taken unmasked SError exception");
+}
+
+static void test_serror_emulated(void)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm = vm_create_with_dabt_handler(&vcpu, test_serror_emulated_guest,
+							unexpected_dabt_handler);
+
+	vm_install_exception_handler(vm, VECTOR_ERROR_CURRENT, expect_serror_handler);
+
+	vcpu_run_expect_sync(vcpu);
+	vcpu_inject_serror(vcpu);
 	vcpu_run_expect_done(vcpu);
 	kvm_vm_free(vm);
 }
···
 	test_mmio_abort();
 	test_mmio_nisv();
 	test_mmio_nisv_abort();
+	test_serror();
+	test_serror_masked();
+	test_serror_emulated();
 }

tools/testing/selftests/kvm/include/arm64/processor.h

···
 	asm volatile("msr daifset, #3" : : : "memory");
 }
 
+static inline void local_serror_enable(void)
+{
+	asm volatile("msr daifclr, #4" : : : "memory");
+}
+
+static inline void local_serror_disable(void)
+{
+	asm volatile("msr daifset, #4" : : : "memory");
+}
+
 /**
  * struct arm_smccc_res - Result from SMC/HVC call
  * @a0-a3 result values from registers 0 to 3