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    SubjectRe: [PATCH] xen/balloon: add late_initcall_sync() for initial ballooning done
    Date
    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@vger.kernel.org>
    >> Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
    >> Signed-off-by: Juergen Gross <jgross@suse.com>
    >
    > 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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