On Mon, Jun 15, 2015 at 10:15:09AM +0200, Thomas Huth wrote: > On Mon, 15 Jun 2015 16:59:08 +1000 > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > On Fri, Jun 05, 2015 at 09:55:55AM +0530, Bharata B Rao wrote: > > > Factor out bits of sPAPR specific CPU initialization code into > > > a separate routine so that it can be called from CPU hotplug > > > path too. > > > > > > While at this, use MSR_EP define instead of using 6 directly. > > > > Don't do this please. MSR[EP] is an obsolete flag from 601. The > > MSR[IP] flag that we're controlling here just happened to re-use the > > same bit position, so using the existing MSR_EP define is misleading. > > Actually, I had the same discussion with Bharata already some weeks ago: > > http://lists.gnu.org/archive/html/qemu-ppc/2015-05/msg00133.html > > > A symbolic name is good, but you should create a new one for MSR[IP] > > instead. > > ... and I had to realize that IP = EP. IP likely stands for "interrupt > prefix" (I guess), and EP simply means "exception prefix", so just two > words for the same meaning. It's just the "on 601" comment in QEMU that > is completely misleading. So IMHO it should be fine to keep the > "MSR_EP" here (and maybe update the comment in cpu.h with a separate > patch?).
I don't entirely agree. Yes EP and IP have related functions - it's
pretty common in ppc history that when an MSR bit is re-used it's for
something similar (for example IS/IR). But MSR[IP] is still a
different name from MSR[EP], and I don't know if the semantics are
identical, though I'm sure they're similar.
--
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
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