On Mon, Apr 13, 2020 at 5:10 PM Jim Mattson <jmattson@xxxxxxxxxx> wrote:
>
> Verify that both injected events and debug traps that result from
> pending debug exceptions take precedence over a "VMX-preemption timer
> expired" VM-exit resulting from a zero-valued VMX-preemption timer.
>
> Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
> Reviewed-by: Oliver Upton <oupton@xxxxxxxxxx>
> Reviewed-by: Peter Shier <pshier@xxxxxxxxxx>
> ---
> x86/vmx_tests.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 120 insertions(+)
>
> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> index 1f97fe3..fccb27f 100644
> --- a/x86/vmx_tests.c
> +++ b/x86/vmx_tests.c
> @@ -8319,6 +8319,125 @@ static void vmx_store_tsc_test(void)
> msr_entry.value, low, high);
> }
>
> +static void vmx_preemption_timer_zero_test_db_handler(struct ex_regs *regs)
> +{
> +}
> +
> +static void vmx_preemption_timer_zero_test_guest(void)
> +{
> + while (vmx_get_test_stage() < 3)
> + vmcall();
> +}
> +
> +static void vmx_preemption_timer_zero_activate_preemption_timer(void)
> +{
> + vmcs_set_bits(PIN_CONTROLS, PIN_PREEMPT);
> + vmcs_write(PREEMPT_TIMER_VALUE, 0);
> +}
> +
> +static void vmx_preemption_timer_zero_advance_past_vmcall(void)
> +{
> + vmcs_clear_bits(PIN_CONTROLS, PIN_PREEMPT);
> + enter_guest();
> + skip_exit_vmcall();
> +}
> +
> +static void vmx_preemption_timer_zero_inject_db(bool intercept_db)
> +{
> + vmx_preemption_timer_zero_activate_preemption_timer();
> + vmcs_write(ENT_INTR_INFO, INTR_INFO_VALID_MASK |
> + INTR_TYPE_HARD_EXCEPTION | DB_VECTOR);
> + vmcs_write(EXC_BITMAP, intercept_db ? 1 << DB_VECTOR : 0);
> + enter_guest();
> +}
> +
> +static void vmx_preemption_timer_zero_set_pending_dbg(u32 exception_bitmap)
> +{
> + vmx_preemption_timer_zero_activate_preemption_timer();
> + vmcs_write(GUEST_PENDING_DEBUG, BIT(12) | DR_TRAP1);
> + vmcs_write(EXC_BITMAP, exception_bitmap);
> + enter_guest();
> +}
> +
> +static void vmx_preemption_timer_zero_expect_preempt_at_rip(u64 expected_rip)
> +{
> + u32 reason = (u32)vmcs_read(EXI_REASON);
> + u64 guest_rip = vmcs_read(GUEST_RIP);
> +
> + report(reason == VMX_PREEMPT && guest_rip == expected_rip,
> + "Exit reason is 0x%x (expected 0x%x) and guest RIP is %lx (0x%lx expected).",
> + reason, VMX_PREEMPT, guest_rip, expected_rip);
> +}
> +
> +/*
> + * This test ensures that when the VMX preemption timer is zero at
> + * VM-entry, a VM-exit occurs after any event injection and after any
> + * pending debug exceptions are raised, but before execution of any
> + * guest instructions.
> + */
> +static void vmx_preemption_timer_zero_test(void)
> +{
> + u64 db_fault_address = (u64)get_idt_addr(&boot_idt[DB_VECTOR]);
> + handler old_db;
> + u32 reason;
> +
> + if (!(ctrl_pin_rev.clr & PIN_PREEMPT)) {
> + report_skip("'Activate VMX-preemption timer' not supported");
> + return;
> + }
> +
> + /*
> + * Install a custom #DB handler that doesn't abort.
> + */
> + old_db = handle_exception(DB_VECTOR,
> + vmx_preemption_timer_zero_test_db_handler);
> +
> + test_set_guest(vmx_preemption_timer_zero_test_guest);
> +
> + /*
> + * VMX-preemption timer should fire after event injection.
> + */
> + vmx_set_test_stage(0);
> + vmx_preemption_timer_zero_inject_db(0);
> + vmx_preemption_timer_zero_expect_preempt_at_rip(db_fault_address);
> + vmx_preemption_timer_zero_advance_past_vmcall();
> +
> + /*
> + * VMX-preemption timer should fire after event injection.
> + * Exception bitmap is irrelevant, since you can't intercept
> + * an event that you injected.
> + */
> + vmx_set_test_stage(1);
> + vmx_preemption_timer_zero_inject_db(1 << DB_VECTOR);
> + vmx_preemption_timer_zero_expect_preempt_at_rip(db_fault_address);
> + vmx_preemption_timer_zero_advance_past_vmcall();
> +
> + /*
> + * VMX-preemption timer should fire after pending debug exceptions
> + * have delivered a #DB trap.
> + */
> + vmx_set_test_stage(2);
> + vmx_preemption_timer_zero_set_pending_dbg(0);
> + vmx_preemption_timer_zero_expect_preempt_at_rip(db_fault_address);
> + vmx_preemption_timer_zero_advance_past_vmcall();
> +
> + /*
> + * VMX-preemption timer would fire after pending debug exceptions
> + * have delivered a #DB trap, but in this case, the #DB trap is
> + * intercepted.
> + */
> + vmx_set_test_stage(3);
> + vmx_preemption_timer_zero_set_pending_dbg(1 << DB_VECTOR);
> + reason = (u32)vmcs_read(EXI_REASON);
> + report(reason == VMX_EXC_NMI, "Exit reason is 0x%x (expected 0x%x)",
> + reason, VMX_EXC_NMI);
> +
> + vmcs_clear_bits(PIN_CONTROLS, PIN_PREEMPT);
> + enter_guest();
> +
> + handle_exception(DB_VECTOR, old_db);
> +}
> +
> static void vmx_db_test_guest(void)
> {
> /*
> @@ -9623,6 +9742,7 @@ struct vmx_test vmx_tests[] = {
> TEST(vmx_pending_event_test),
> TEST(vmx_pending_event_hlt_test),
> TEST(vmx_store_tsc_test),
> + TEST(vmx_preemption_timer_zero_test),
> /* EPT access tests. */
> TEST(ept_access_test_not_present),
> TEST(ept_access_test_read_only),
> --
> 2.26.0.110.g2183baf09c-goog
Adding +Paolo Bonzini.
