Re: [kvm-unit-tests PATCH v3 5/5] x86: VMX: Add tests for monitor trap flag

[Paolo Bonzini <pbonzini@redhat.com>]

On 25/02/20 01:09, Oliver Upton wrote:
> On Fri, Feb 7, 2020 at 2:36 AM Oliver Upton <oupton@google.com> wrote:
>>
>> Test to verify that MTF VM-exits into host are synthesized when the
>> 'monitor trap flag' processor-based VM-execution control is set under
>> various conditions.
>>
>> Expect an MTF VM-exit if instruction execution produces no events other
>> than MTF. Should instruction execution produce a concurrent debug-trap
>> and MTF event, expect an MTF VM-exit with the 'pending debug exceptions'
>> VMCS field set. Expect an MTF VM-exit to follow event delivery should
>> instruction execution generate a higher-priority event, such as a
>> general-protection fault. Lastly, expect an MTF VM-exit to follow
>> delivery of a debug-trap software exception (INT1/INT3/INTO/INT n).
>>
>> Signed-off-by: Oliver Upton <oupton@google.com>
>> Reviewed-by: Jim Mattson <jmattson@google.com>
>> ---
>>  x86/vmx.h       |   1 +
>>  x86/vmx_tests.c | 157 ++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 158 insertions(+)
>>
>> diff --git a/x86/vmx.h b/x86/vmx.h
>> index 6214400f2b53..6adf0916564b 100644
>> --- a/x86/vmx.h
>> +++ b/x86/vmx.h
>> @@ -399,6 +399,7 @@ enum Ctrl0 {
>>         CPU_NMI_WINDOW          = 1ul << 22,
>>         CPU_IO                  = 1ul << 24,
>>         CPU_IO_BITMAP           = 1ul << 25,
>> +       CPU_MTF                 = 1ul << 27,
>>         CPU_MSR_BITMAP          = 1ul << 28,
>>         CPU_MONITOR             = 1ul << 29,
>>         CPU_PAUSE               = 1ul << 30,
>> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
>> index b31c360c5f3c..0e2c2f8a7d34 100644
>> --- a/x86/vmx_tests.c
>> +++ b/x86/vmx_tests.c
>> @@ -4970,6 +4970,162 @@ static void test_vmx_preemption_timer(void)
>>         vmcs_write(EXI_CONTROLS, saved_exit);
>>  }
>>
>> +extern unsigned char test_mtf1;
>> +extern unsigned char test_mtf2;
>> +extern unsigned char test_mtf3;
>> +
>> +__attribute__((noclone)) static void test_mtf_guest(void)
>> +{
>> +       asm ("vmcall;\n\t"
>> +            "out %al, $0x80;\n\t"
>> +            "test_mtf1:\n\t"
>> +            "vmcall;\n\t"
>> +            "out %al, $0x80;\n\t"
>> +            "test_mtf2:\n\t"
>> +            /*
>> +             * Prepare for the 'MOV CR3' test. Attempt to induce a
>> +             * general-protection fault by moving a non-canonical address into
>> +             * CR3. The 'MOV CR3' instruction does not take an imm64 operand,
>> +             * so we must MOV the desired value into a register first.
>> +             *
>> +             * MOV RAX is done before the VMCALL such that MTF is only enabled
>> +             * for the instruction under test.
>> +             */
>> +            "mov $0x8000000000000000, %rax;\n\t"
>> +            "vmcall;\n\t"
>> +            "mov %rax, %cr3;\n\t"
>> +            "test_mtf3:\n\t"
>> +            "vmcall;\n\t"
>> +            /*
>> +             * ICEBP/INT1 instruction. Though the instruction is now
>> +             * documented, don't rely on assemblers enumerating the
>> +             * instruction. Resort to hand assembly.
>> +             */
>> +            ".byte 0xf1;\n\t");
>> +}
>> +
>> +static void test_mtf_gp_handler(struct ex_regs *regs)
>> +{
>> +       regs->rip = (unsigned long) &test_mtf3;
>> +}
>> +
>> +static void test_mtf_db_handler(struct ex_regs *regs)
>> +{
>> +}
>> +
>> +static void enable_mtf(void)
>> +{
>> +       u32 ctrl0 = vmcs_read(CPU_EXEC_CTRL0);
>> +
>> +       vmcs_write(CPU_EXEC_CTRL0, ctrl0 | CPU_MTF);
>> +}
>> +
>> +static void disable_mtf(void)
>> +{
>> +       u32 ctrl0 = vmcs_read(CPU_EXEC_CTRL0);
>> +
>> +       vmcs_write(CPU_EXEC_CTRL0, ctrl0 & ~CPU_MTF);
>> +}
>> +
>> +static void enable_tf(void)
>> +{
>> +       unsigned long rflags = vmcs_read(GUEST_RFLAGS);
>> +
>> +       vmcs_write(GUEST_RFLAGS, rflags | X86_EFLAGS_TF);
>> +}
>> +
>> +static void disable_tf(void)
>> +{
>> +       unsigned long rflags = vmcs_read(GUEST_RFLAGS);
>> +
>> +       vmcs_write(GUEST_RFLAGS, rflags & ~X86_EFLAGS_TF);
>> +}
>> +
>> +static void report_mtf(const char *insn_name, unsigned long exp_rip)
>> +{
>> +       unsigned long rip = vmcs_read(GUEST_RIP);
>> +
>> +       assert_exit_reason(VMX_MTF);
>> +       report(rip == exp_rip, "MTF VM-exit after %s instruction. RIP: 0x%lx (expected 0x%lx)",
>> +              insn_name, rip, exp_rip);
>> +}
>> +
>> +static void vmx_mtf_test(void)
>> +{
>> +       unsigned long pending_dbg;
>> +       handler old_gp, old_db;
>> +
>> +       if (!(ctrl_cpu_rev[0].clr & CPU_MTF)) {
>> +               printf("CPU does not support the 'monitor trap flag' processor-based VM-execution control.\n");
>> +               return;
>> +       }
>> +
>> +       test_set_guest(test_mtf_guest);
>> +
>> +       /* Expect an MTF VM-exit after OUT instruction */
>> +       enter_guest();
>> +       skip_exit_vmcall();
>> +
>> +       enable_mtf();
>> +       enter_guest();
>> +       report_mtf("OUT", (unsigned long) &test_mtf1);
>> +       disable_mtf();
>> +
>> +       /*
>> +        * Concurrent #DB trap and MTF on instruction boundary. Expect MTF
>> +        * VM-exit with populated 'pending debug exceptions' VMCS field.
>> +        */
>> +       enter_guest();
>> +       skip_exit_vmcall();
>> +
>> +       enable_mtf();
>> +       enable_tf();
>> +
>> +       enter_guest();
>> +       report_mtf("OUT", (unsigned long) &test_mtf2);
>> +       pending_dbg = vmcs_read(GUEST_PENDING_DEBUG);
>> +       report(pending_dbg & DR_STEP,
>> +              "'pending debug exceptions' field after MTF VM-exit: 0x%lx (expected 0x%lx)",
>> +              pending_dbg, (unsigned long) DR_STEP);
>> +
>> +       disable_mtf();
>> +       disable_tf();
>> +       vmcs_write(GUEST_PENDING_DEBUG, 0);
>> +
>> +       /*
>> +        * #GP exception takes priority over MTF. Expect MTF VM-exit with RIP
>> +        * advanced to first instruction of #GP handler.
>> +        */
>> +       enter_guest();
>> +       skip_exit_vmcall();
>> +
>> +       old_gp = handle_exception(GP_VECTOR, test_mtf_gp_handler);
>> +
>> +       enable_mtf();
>> +       enter_guest();
>> +       report_mtf("MOV CR3", (unsigned long) get_idt_addr(&boot_idt[GP_VECTOR]));
>> +       disable_mtf();
>> +
>> +       /*
>> +        * Concurrent MTF and privileged software exception (i.e. ICEBP/INT1).
>> +        * MTF should follow the delivery of #DB trap, though the SDM doesn't
>> +        * provide clear indication of the relative priority.
>> +        */
>> +       enter_guest();
>> +       skip_exit_vmcall();
>> +
>> +       handle_exception(GP_VECTOR, old_gp);
>> +       old_db = handle_exception(DB_VECTOR, test_mtf_db_handler);
>> +
>> +       enable_mtf();
>> +       enter_guest();
>> +       report_mtf("INT1", (unsigned long) get_idt_addr(&boot_idt[DB_VECTOR]));
>> +       disable_mtf();
>> +
>> +       enter_guest();
>> +       handle_exception(DB_VECTOR, old_db);
>> +}
>> +
>>  /*
>>   * Tests for VM-execution control fields
>>   */
>> @@ -9505,5 +9661,6 @@ struct vmx_test vmx_tests[] = {
>>         TEST(atomic_switch_max_msrs_test),
>>         TEST(atomic_switch_overflow_msrs_test),
>>         TEST(rdtsc_vmexit_diff_test),
>> +       TEST(vmx_mtf_test),
>>         { NULL, NULL, NULL, NULL, NULL, {0} },
>>  };
>> --
>> 2.25.0.341.g760bfbb309-goog
>>
> 
> Friendly ping :) (Just on this patch, 1-4 have already been applied)

Done, thanks.  I only had to push, since I had applied it already to
test the KVM changes.

Paolo