Re: [Qemu-devel] [PATCH 00/17] ppc: preparing pnv landing

[David Gibson]

On Thu, Mar 17, 2016 at 03:28:46PM +0100, Cédric Le Goater wrote:
> On 03/17/2016 03:45 AM, David Gibson wrote:
> > On Wed, Mar 16, 2016 at 10:08:19AM +0100, Cédric Le Goater wrote:
> >> On 03/16/2016 02:19 AM, David Gibson wrote:
> >>> On Tue, Mar 15, 2016 at 09:11:31AM +0100, Cédric Le Goater wrote:
> >>>> On 03/15/2016 01:39 AM, David Gibson wrote:
> >>>>> On Mon, Mar 14, 2016 at 05:56:23PM +0100, Cédric Le Goater wrote:
> >>>>>> Hello,
> >>>>>>
> >>>>>> This is a first mini-serie of patches adding support for new ppc SPRs.
> >>>>>> They were taken from Ben's larger patchset adding the ppc powernv
> >>>>>> platform and they should already be useful for the pseries guest
> >>>>>> migration.
> >>>>>>
> >>>>>> Initial patches come from :
> >>>>>>
> >>>>>>        https://github.com/ozbenh/qemu/commits/powernv
> >>>>>>
> >>>>>> The changes are mostly due to the rebase on Dave's 2.6 branch:
> >>>>>>
> >>>>>>        https://github.com/dgibson/qemu/commits/ppc-for-2.6
> >>>>>>
> >>>>>> A couple more are bisect and checkpatch fixes and finally some patches
> >>>>>> were merge to reduce the noise.
> >>>>>>
> >>>>>>       
> >>>>>>
> >>>>>> The patchset is also available here: 
> >>>>>>
> >>>>>>        https://github.com/legoater/qemu/commits/for-2.6
> >>>>>>
> >>>>>> It was quickly tested with a pseries guest using KVM and TCG.
> >>>>>
> >>>>> Hmm.. do these all fix bugs with migration, or only some of them?
> >>>>
> >>>> Probably only some. 
> >>>>
> >>>> Initially, Thomas gave a shorter list which I expanded to a larger one 
> >>>> because of dependencies between patches and I didn't want to change too
> >>>> much what Ben had sent. You had also reviewed a few.
> >>>>
> >>>>> The relevance is that things to fix migration should go into 2.6, but
> >>>>> preparation work for powernv that doesn't fix bug shouldn't really be
> >>>>> going in now, after the soft freeze and will need to wait for 2.7.
> >>>>
> >>>> OK. I will rework and keep the rest for 2.7. 
> >>>
> >>> So, I'm ok with including (low risk) patches that aren't directly
> >>> relevant to 2.6 if they're prereqs for patches that are relevant to
> >>> 2.6.  After all, reworking the patches isn't risk free either.  Please
> >>> mention why these patches are being included in the commit messages
> >>> though.
> >>
> >> Sure.  
> >>
> >>>> Thomas, thanks for the review. I have identified a few things I need 
> >>>> to work on but may be, the patchset is still too large for 2.6 ?
> >>>
> >>> It's not really a question of being too large, it's that I'm nervous
> >>> about applying patches which touch the core translation code
> >>> (e.g. fixes to HV mode tests) during soft freeze if they're not
> >>> addressing a bug that's relevant to 2.6.
> >>
> >> Could you please take a look at these two patches to see if they are 
> >> relevant for 2.6 ? From my readings, they seem to be the only ones on 
> >> the edge.
> >>
> >>    06/17  ppc: Create cpu_ppc_set_papr() helper 
> >>    11/17  ppc: Initialize AMOR in PAPR mode  
> > 
> > Ok, I've replied to each of those.
> > 
> >> but it makes sense to take them if we take :
> >>
> >>    12/17  ppc: Fix writing to AMR/UAMOR (move hunk to 13)
> > 
> > I'm not seeing a lot of cause to put this in for 2.6.  The registers
> > in question are already linked up to KVM, so migration should be ok,
> > and I don't believe we have real use cases which are hitting the bugs
> > this patch fixes.  Except...
> > 
> >>    13/17  ppc: Add POWER8 IAMR register (rework hunk)
> > 
> > ..that I guess it's kind of a pre-req for this one, which could fix real
> > migration bugs.
> 
> Yes. So, I will send a v3 removing the LPCR changes in the cpu_ppc_set_papr()
> helper. How does that sound ? 

Ok, sounds good.

-- 
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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