Re: [RFC PATCH] emulator: Fix task switch into/out of VM86

[Gleb Natapov <gleb@redhat.com>]

On Tue, Jan 10, 2012 at 12:25:18PM +0100, Kevin Wolf wrote:
> Am 10.01.2012 10:28, schrieb Kevin Wolf:
> > Am 10.01.2012 10:01, schrieb Gleb Natapov:
> >> On Mon, Jan 09, 2012 at 09:10:10PM +0100, Kevin Wolf wrote:
> >>> * This works with VMX, but with SVM I have an additional problem: When
> >>>   trying to exit VM86 (usually by an exception) through a task gate in
> >>>   the IDT, the code runs into the reason = TASK_SWITCH_CALL path. I
> >>>   searched a bit in the documentation, but didn't find any obvious way
> >>>   to fix this.
> >>>
> >> Hmm, so exit_int_info is invalid during task switch exit even though
> >> task switch was caused by an exception. I wonder is this the case when
> >> vcpu is not in vm86 mode too?
> > 
> > No idea, I would have to try it out.
> 
> Did that now, and it looks like exit_int_info is always 0 during the
> task switch intercept for a task gate in the IDT. So special-casing VM86
> won't help, I'm afraid.
> 
Joerg, do you know how can we check that task switch was cause by an
exception triggering task gate if exit_int_info is not provided during
intercept (short of decoding instruction that caused intercept to see if
it's a call to a gate, which is racy) ?

--
			Gleb.