Re: [PATCH v4] xen/balloon: add late_initcall_sync() for initial ballooning done

[Boris Ostrovsky]

On 11/2/21 5:19 AM, 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.
>
> Warn on console if initial ballooning fails, panic() after stalling
> for more than 3 minutes per default. Add a module parameter for
> changing this timeout.
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>



Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>