Re: [PATCH v4 1/4] KVM: Dynamic sized kvm memslots array

[Peter Xu]

On Mon, Oct 21, 2024 at 10:05:23PM +0300, Michael Tokarev wrote:
> 21.10.2024 17:37, Peter Xu wrote:
> > Michael,
> > 
> > On Fri, Oct 18, 2024 at 06:38:53PM +0300, Michael Tokarev wrote:
> > > Looking at this from qemu-stable PoV, I'm not 100% sure this change is 
> > > good
> > > for stable-7.2 series, because 7.2 lacks v8.1.0-1571-g5b23186a95
> > > "kvm: Return number of free memslots" commit, which was a preparation for
> > > for memory devices that consume multiple memslots.
> > > 
> > > I did a backport of this change (currently it is at the tip of staging-7.2
> > > branch of https://gitlab.com/mjt0k/qemu.git) - I had to tweak context and
> > > also to remove now-unused local variable in kvm-all.c.  It builds and the
> > > tests run fine, but I'm not really sure it does what it is intended to do.
> > > 
> > > Should anything else be picked up for 7.2 for all this to work, or should
> > > this change not be back-ported to 7.2 ?
> > > 
> > > (for more recent releases, everything looks ok).
> > 
> > I don't remember anything this series logically depends on (besides any
> > context-wise change).
> 
> Well, 7.2 is a bit old by now, and the commit I already mentioned above is
> also quite old, - at the time you started working on this series, this
> commit (v8.1.0-1571-g5b23186a95) has been in the tree for a long time
> already.  This change might be relevant here or might be not.

That specific commit (5b23186a95) shouldn't be relevant.

> 
> > If there's uncertainty / challenge from backporting to some stable branches
> > from your POV, we can still keep things simple and skip the series, as it's
> > only a perf regression and only happens during live migrations (which can
> > enlarge the downtime, for example) but not daily VM use.
> 
> For this change alone, I did the backport, I just am not sure it makes sense.
> 
> It would be great if you take a look, including the change I mentioned above
> (it isn't in 7.2), there: https://gitlab.com/mjt0k/qemu/-/commits/staging-7.2
> Or we can just drop it for 7.2 per the above.

I checked the backport, it looks all good.

Thanks,

-- 
Peter Xu