Re: [PATCH 05/11] KVM: PPC: add GPR RA update skeleton for MMIO emulation

[Simon Guo <wei.guo.simon@gmail.com>]

On Thu, May 03, 2018 at 03:58:14PM +1000, Paul Mackerras wrote:
> On Wed, Apr 25, 2018 at 07:54:38PM +0800, wei.guo.simon@gmail.com wrote:
> > From: Simon Guo <wei.guo.simon@gmail.com>
> > 
> > To optimize kvm emulation code with analyse_instr, adds new
> > mmio_update_ra flag to aid with GPR RA update.
> > 
> > This patch arms RA update at load/store emulation path for both
> > qemu mmio emulation or coalesced mmio emulation.
> 
> It's not clear to me why you need to do this.  The existing code
> writes RA at the point where the instruction is decoded.  In later
> patches, you change that so the RA update occurs after the MMIO
> operation is performed.  Is there a particular reason why you made
> that change?
> 
> Paul.

I wanted to avoid the case that GPR RA was updated even when EMULATE_FAIL. But
if it is not mandatory, I can update RA in kvmppc_emulate_loadstore()
instead..

Thanks,
- Simon