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

Chao Gao
2024-05-28T07:46:20Z

>+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
>
>