Subject: Re: [PATCH v3] powerpc/kvm: support to handle sw breakpoint

From: Madhavan Srinivasan <[email-masked]>
Date: Tue, 12 Aug 2014 10:47:55 +0530

On Monday 11 August 2014 02:45 PM, Alexander Graf wrote:
> 
> On 11.08.14 10:51, Benjamin Herrenschmidt wrote:
>> On Mon, 2014-08-11 at 09:26 +0200, Alexander Graf wrote:
>>>> diff --git a/arch/powerpc/kvm/emulate.c b/arch/powerpc/kvm/emulate.c
>>>> index da86d9b..d95014e 100644
>>>> --- a/arch/powerpc/kvm/emulate.c
>>>> +++ b/arch/powerpc/kvm/emulate.c
>>> This should be book3s_emulate.c.
>> Any reason we can't make that 00dddd00 opcode as breakpoint common to
>> all powerpc variants ?
> 
> I can't think of a good reason. We use a hypercall on booke (which traps
> into an illegal instruction for pr) today, but I don't think it has to
> be that way.
> 
> Given that the user space API allows us to change it dynamically, there
> should be nothing blocking us from going with 00dddd00 always.
> 
Kindly correct me if i am wrong. So we can still have a common code in
emulate.c to set the env for both HV and pr incase of illegal
instruction (i will rebase latest src). But suggestion here to use
00dddd00, in that case current path in embed is kvmppc_handle_exit
(booke.c) -> BOOKE_INTERRUPT_HV_PRIV -> emulation_exit ->
kvmppc_emulate_instruction, will change to kvmppc_handle_exit (booke.c)
-> BOOKE_INTERRUPT_PROGRAM -> if debug instr call emulation_exit else
send to guest?

Thanks for review
regards
Maddy

> Alex