From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [PATCH] test: Add emulator test for iret instruction
Date: Wed, 28 Jul 2010 17:32:18 -0300
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To: Mohammed Gamal <m.gamal005@gmail.com>
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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@redhat.co=
m> 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 instruct=
ion
> >>
> >> Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
> >>
> >> ---
> >> Changes from v1:
> >> - Added test for 16-bit iret
> >> - Added tests for returned eflags
> >> ---
> >> =A0kvm/test/x86/realmode.c | =A0 79 ++++++++++++++++++++++++++++++=
+++++++++++++++++
> >> =A01 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()
> >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 print_serial("Pusha/Popa Test2: PASS\n=
");
> >> =A0}
> >>
> >> +void test_iret()
> >> +{
> >> + =A0 =A0 struct regs inregs =3D { 0 }, outregs;
> >> +
> >> + =A0 =A0 MK_INSN(iret32, "pushf\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "pushl %cs\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "call 1f\n\t" /* a near =
call will push eip onto the stack */
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "jmp 2f\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "1: iret\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "2:\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0);
> >> +
> >> + =A0 =A0 MK_INSN(iret16, "pushfw\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "pushw %cs\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "callw 1f\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "jmp 2f\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "1: iretw\n\t"
> >> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "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.