On Wed, Jul 28, 2010 at 11:32 PM, Marcelo Tosatti <mtosatti@xxxxxxxxxx> wrote:
> On Wed, Jul 28, 2010 at 11:28:05PM +0300, Mohammed Gamal wrote:
>> On Wed, Jul 28, 2010 at 10:55 PM, Marcelo Tosatti <mtosatti@xxxxxxxxxx> wrote:
>> > On Wed, Jul 28, 2010 at 12:39:01PM +0300, Mohammed Gamal wrote:
>> >> This adds a unit test for real mode emulation of the iret instruction
>> >>
>> >> Signed-off-by: Mohammed Gamal <m.gamal005@xxxxxxxxx>
>> >>
>> >> ---
>> >> Changes from v1:
>> >> - Added test for 16-bit iret
>> >> - Added tests for returned eflags
>> >> ---
>> >> kvm/test/x86/realmode.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++
>> >> 1 files changed, 79 insertions(+), 0 deletions(-)
>> >>
>> >> diff --git a/kvm/test/x86/realmode.c b/kvm/test/x86/realmode.c
>> >> index bd79348..74456c3 100644
>> >> --- a/kvm/test/x86/realmode.c
>> >> +++ b/kvm/test/x86/realmode.c
>> >> @@ -865,6 +865,84 @@ void test_pusha_popa()
>> >> print_serial("Pusha/Popa Test2: PASS\n");
>> >> }
>> >>
>> >> +void test_iret()
>> >> +{
>> >> + struct regs inregs = { 0 }, outregs;
>> >> +
>> >> + MK_INSN(iret32, "pushf\n\t"
>> >> + "pushl %cs\n\t"
>> >> + "call 1f\n\t" /* a near call will push eip onto the stack */
>> >> + "jmp 2f\n\t"
>> >> + "1: iret\n\t"
>> >> + "2:\n\t"
>> >> + );
>> >> +
>> >> + MK_INSN(iret16, "pushfw\n\t"
>> >> + "pushw %cs\n\t"
>> >> + "callw 1f\n\t"
>> >> + "jmp 2f\n\t"
>> >> + "1: iretw\n\t"
>> >> + "2:\n\t");
>> >
>> > Unless iret causes a task switch, it will not cause an exit.
>> >
>> >
>> The test covers only the real mode case, we won't have a task switch there, no?
>
> No. And there is no vmexit for iret, so it does not go through the
> emulator.
>
I'm pretty sure the iret instruction went through the emulator. I saw
the instruction opcode (0xcf) being in ftrace.
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