Re: [Qemu-devel] [PATCH v6 08/10] target-arm: A64: Emulate the SMC insn

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Fri, Sep 26, 2014 at 12:43:40AM +0100, Peter Maydell wrote:
> On 26 September 2014 00:31, Edgar E. Iglesias <edgar.iglesias@gmail.com> wrote:
> > On Fri, Sep 26, 2014 at 12:17:59AM +0100, Peter Maydell wrote:
> >> Oh, yes, that's the trap enable bit. In that case we shouldn't
> >> be using EXCP_SMC: this isn't routing the SMC exception, it's
> >> taking a Hyp trap exception, and in AArch32 the vector
> >> entry point is different. (Granted, you can't get to AArch32
> >> by taking an exception from AArch64, but we should use the
> >> right EXCP_ value to avoid the code looking gratuitously
> >> different for the two cases.)
> >
> > I see. I hadn't thought much about the AArch32 case here. For
> > AArch64, the pseudo code referes to this as route_to_el2.
> 
> Mmm, but the pseudocode keeps AArch64 and AArch32 exception
> paths a lot more separate than we do, and so it doesn't need
> any information about the AArch32 exception when it's dealing
> with a from-AArch64 exception. Our implementation routes
> both paths in common, and so it's slightly clearer to always
> retain the correct info for both cases (if nothing else, it's
> slightly more accurate when we print out debug log about
> what exceptions we're taking).

Agreed, your suggestion makes sense and will save some
pain for the A32 case. Good catch, thanks.

> 
> > Anyway, your comment makes sense to avoid diff between a32/a64
> > and I think it actually makes the AArch64 code a bit cleaner
> > aswell.
> >
> > I'll add EXCP_HYP_TRAP.
> 
> Thanks.
> 
> -- PMM