Re: [Qemu-ppc] [PATCH 0/5] Improve balloon handling of pagesizes other than 4kiB

[Michael S. Tsirkin]

On Tue, Mar 05, 2019 at 11:53:32AM +1100, David Gibson wrote:
> On Thu, Feb 28, 2019 at 08:39:21AM -0500, Michael S. Tsirkin wrote:
> > On Thu, Feb 14, 2019 at 03:39:11PM +1100, David Gibson wrote:
> > > I posted some RFCs for this back in December, but didn't wrap it up in
> > > time for 3.1.  Posting again for inclusion in 4.0.
> > > 
> > > The virtio-balloon devices was never really thought out for cases
> > > other than 4kiB pagesize on both guest and host.  It works in some
> > > cases, but in others can be ineffectual or even cause guest memory
> > > corruption.
> > > 
> > > This series makes a handful of preliminary cleanups, then makes a
> > > change to safely, though not perfectly, handle cases with non 4kiB
> > > pagesizes.
> > 
> > I'd like to see a version of this that does not depend on patch 1 which
> > is not a cleanup nor a bugfix. Could you look into this please?
> 
> Ok... the original series is already applied to master, so I'm not
> exactly sure what you want me to do here.  Should I try to come up
> with a "logical revert" of the first patch?  Or do you intend to
> revert the whole series, and I rewrite the series without the first
> patch?

Whatever you prefer. Maybe the best idea is to add a flag
that says whether to madvise or not. Default can be compatible.
Hmm?


> > We can then debate merits of patch 1 separately.
> > 
> > 
> > > Changes since RFC:
> > >  * Further refinement of when to issue warnings in 5/5
> > > 
> > > David Gibson (5):
> > >   virtio-balloon: Remove unnecessary MADV_WILLNEED on deflate
> > >   virtio-balloon: Corrections to address verification
> > >   virtio-balloon: Rework ballon_page() interface
> > >   virtio-balloon: Use ram_block_discard_range() instead of raw madvise()
> > >   virtio-balloon: Safely handle BALLOON_PAGE_SIZE < host page size
> > > 
> > >  hw/virtio/virtio-balloon.c         | 102 ++++++++++++++++++++++++-----
> > >  include/hw/virtio/virtio-balloon.h |   3 +
> > >  2 files changed, 89 insertions(+), 16 deletions(-)
> > > 
> > 
> 
> -- 
> 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