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

+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