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

[David Gibson]

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.

-- 
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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