linux-kernel - Re: [PATCH v4] xen/balloon: add late_initcall

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Message-ID: <f986a7c4-3032-fecd-2e19-4d63a2ee10c7@oracle.com>
Date:   Wed, 3 Nov 2021 21:55:05 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Juergen Gross <jgross@...e.com>, xen-devel@...ts.xenproject.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Jonathan Corbet <corbet@....net>,
        Stefano Stabellini <sstabellini@...nel.org>,
        stable@...r.kernel.org,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
Subject: Re: [PATCH v4] xen/balloon: add late_initcall_sync() for initial
 ballooning done


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@...r.kernel.org>
> Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
> Signed-off-by: Juergen Gross <jgross@...e.com>



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