Re: [PATCH v3 5/5] KVM: selftests: KVM: SVM: Add Idle HLT intercept test

[Chao Gao <chao.gao@intel.com>]

>+static void guest_code(void)
>+{
>+	uint32_t icr_val;
>+	int i;
>+
>+	xapic_enable();
>+
>+	icr_val = (APIC_DEST_SELF | APIC_INT_ASSERT | VINTR_VECTOR);
>+
>+	for (i = 0; i < NUM_ITERATIONS; i++) {
>+		cli();
>+		xapic_write_reg(APIC_ICR, icr_val);
>+		safe_halt();
>+		GUEST_ASSERT(READ_ONCE(irq_received));
>+		WRITE_ONCE(irq_received, false);

any reason to use READ/WRITE_ONCE here?

>+	}
>+	GUEST_DONE();
>+}
>+
>+static void guest_vintr_handler(struct ex_regs *regs)
>+{
>+	WRITE_ONCE(irq_received, true);
>+	xapic_write_reg(APIC_EOI, 0x00);
>+}
>+
>+int main(int argc, char *argv[])
>+{
>+	struct kvm_vm *vm;
>+	struct kvm_vcpu *vcpu;
>+	struct ucall uc;
>+	uint64_t  halt_exits, vintr_exits;
>+
>+	/* Check the extension for binary stats */
>+	TEST_REQUIRE(this_cpu_has(X86_FEATURE_IDLE_HLT));

IIUC, this test assumes that the IDLE_HLT feature is enabled for guests if it
is supported by the CPU. But this isn't true in some cases:

1. an old KVM runs on new hardware
2. the feature bit is somehow cleared, e.g., by "clearcpuid" cmdline


>+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_BINARY_STATS_FD));
>+
>+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
>+
>+	vm_install_exception_handler(vm, VINTR_VECTOR, guest_vintr_handler);
>+	virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
>+
>+	vcpu_run(vcpu);
>+	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
>+
>+	halt_exits = vcpu_get_stat(vcpu, HALT_EXITS);
>+	vintr_exits = vcpu_get_stat(vcpu, IRQ_WINDOW_EXITS);
>+
>+	switch (get_ucall(vcpu, &uc)) {
>+	case UCALL_ABORT:
>+		REPORT_GUEST_ASSERT(uc);
>+		/* NOT REACHED */
>+	case UCALL_DONE:
>+		break;
>+
>+	default:
>+		TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
>+	}
>+
>+	TEST_ASSERT_EQ(halt_exits, 0);
>+	pr_debug("Guest executed VINTR followed by halts: %d times.\n"
>+		 "The guest exited due to halt: %ld times and number\n"
>+		 "of vintr exits: %ld.\n",
>+		 NUM_ITERATIONS, halt_exits, vintr_exits);
>+
>+	kvm_vm_free(vm);
>+	return 0;
>+}
>-- 
>2.34.1
>
>