Re: [Qemu-devel] [Qemu-ppc] [PATCH 47/58] Implement POWER7's CFAR in TCG

[David Gibson]

On Sat, Sep 17, 2011 at 05:08:29PM +0000, Blue Swirl wrote:
> On Wed, Sep 14, 2011 at 8:43 AM, Alexander Graf <address@hidden> wrote:
> > From: David Gibson <address@hidden>
> >
> > This patch implements support for the CFAR SPR on POWER7 (Come From
> > Address Register), which snapshots the PC value at the time of a branch or
> > an rfid.  The latest powerpc-next kernel also catches it and can show it in
> > xmon or in the signal frames.
> >
> > This works well enough to let recent kernels boot (which otherwise oops
> > on the CFAR access).  It hasn't been tested enough to be confident that the
> > CFAR values are actually accurate, but one thing at a time.
> 
> This looks accurate at least for the cases covered.
> 
> A higher performance implementation could be to only update the
> register lazily when the SPR is read, in most other times CFAR would
> be only stored to DisasContext.

Uh, yeah.  I think I'll leave that to someone who actually understands
TCG, rather than just bluffing it.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson