Subject: Re: [PATCH] KVM: PPC: Book3S: Add support for H_IPOLL and H_XIRR_X in XICS emulation

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 30 May 2013 09:57:32 +1000

On Wed, 2013-05-29 at 18:38 -0500, Scott Wood wrote:

> > Yes. I'd like to have them in. Their implementation is actually fairly
> > trivial and they cannot be emulated by qemu if the rest of the XICS is
> > in the kernel, so it's a problem.
> 
> OK.  Does it make more sense for you to take it as Paul suggested, or  
> for Gleb or Marcelo to pick it up directly?

I'll take it.

> Then rm_action should always be 0 for these hcalls, right?  So there's  
> no correctness reason to keep the hcalls in separate switch  
> statements.  You shave off a few cycles checking rm_action, at the cost  
> of needing to change kvmppc_xics_hcall() if a real-mode version of  
> these hcalls is ever done.

No, because rm_action will also be 0 if the hcall was fully done in real
mode (which can happen, that's our fast path), in which case we do *NOT*
want to to be re-done in virtual mode.

That's why we always return whether rm_action is 0 or not when real-mode
is enabled.

Cheers,
Ben.