Re: [PATCH] xen/balloon: add late_initcall_sync() for initial ballooning done

[Juergen Gross <jgross@xxxxxxxx>]

On 28.10.21 22:16, Marek Marczykowski-Górecki wrote:
> On Thu, Oct 28, 2021 at 12:59:52PM +0200, Juergen Gross wrote:
> > When running as PVH or HVM guest with actual memory < max memory the
> > hypervisor is using "populate on demand" in order to allow the guest
> > to balloon down from its maximum memory size. For this to work
> > correctly the guest must not touch more memory pages than its target
> > memory size as otherwise the PoD cache will be exhausted and the guest
> > is crashed as a result of that.
> >
> > In extreme cases ballooning down might not be finished today before
> > the init process is started, which can consume lots of memory.
> >
> > In order to avoid random boot crashes in such cases, add a late init
> > call to wait for ballooning down having finished for PVH/HVM guests.
> >
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> It may happen that initial balloon down fails (state==BP_ECANCELED). In
> that case, it waits indefinitely. I think it should rather report a
> failure (and panic? it's similar to OOM before PID 1 starts, so rather
> hard to recover), instead of hanging.
Okay, I can add something like that. I'm thinking of issuing a failure
message in case of credit not having changed for 1 minute and panic()
after two more minutes. Is this fine?


Juergen

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