Re: [Xen-devel] [PATCH] vmx: Allow software (user defined) interrupts to be injected in to the guest

["Dong, Eddie" <eddie.dong@xxxxxxxxx>]

> > The TRAP_debug should not use SW_EXCEPTION, it should use
> HW_EXCEPTION
> > Per SDM and confirmation from our HW guys. We will send fixes soon.
> 
> Please also have the opcode 0xF1 generated #DB addressed in
> whatever is the appropriate way.

Opcode 0xf1 should use " privileged software exception".

What we can do probably include:
1: A patch to fix the mistake of #BP & #OF, plus additional comments to state 
the usage of the API.
2: Another patch to provide a new API for 0xf1 & CD nn? But we don't have real 
usage case to test so far.

We will provide #1 quickly, but for #2, can Aravindh provide test if we get the 
patch ready?

> 
> >>
> >> Anyone except perhaps LOCK - none of them should have any effect
> >> other than making the instruction longer.
> >>
> > LOCK can never be used as prefix of INT nn instruction, nor can REPx
> prefix.
> > Can you provide more details as for this concern?
> 
> The only prefix that is documented to cause #UD here is LOCK. All

In #UD case (fault), the guest RIP is not advanced per SDM, and therefore guest 
will either 
spin in the previous LOCK instruction, or advance the IP to next instruction by 
guest #UD handler.
I didn't see emulator could advance IP to the next instruction (INT nn) for 
LOCK prefix.
Do I miss something?

> other prefixes should consequently be considered ignored, and so
> should the emulation do (and properly handle resulting instruction
> lengths).
> 
The behavior is un-defined per SDM in this case, so either solution should be 
fine :)

Thx, Eddie

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