From: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
To: Juergen Gross <jgross@suse.com>
Cc: xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Stefano Stabellini <sstabellini@kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH] xen/balloon: add late_initcall_sync() for initial ballooning done
Date: Thu, 28 Oct 2021 22:16:59 +0200 [thread overview]
Message-ID: <YXsFO2TMRiJTQM2q@mail-itl> (raw)
In-Reply-To: <20211028105952.10011-1-jgross@suse.com>
[-- Attachment #1: Type: text/plain, Size: 2186 bytes --]
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.
Anyway, it does fix the boot crashes.
> ---
> drivers/xen/balloon.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 3a50f097ed3e..d19b851c3d3b 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -765,3 +765,23 @@ static int __init balloon_init(void)
> return 0;
> }
> subsys_initcall(balloon_init);
> +
> +static int __init balloon_wait_finish(void)
> +{
> + if (!xen_domain())
> + return -ENODEV;
> +
> + /* PV guests don't need to wait. */
> + if (xen_pv_domain() || !current_credit())
> + return 0;
> +
> + pr_info("Waiting for initial ballooning down having finished.\n");
> +
> + while (current_credit())
> + schedule_timeout_interruptible(HZ / 10);
> +
> + pr_info("Initial ballooning down finished.\n");
> +
> + return 0;
> +}
> +late_initcall_sync(balloon_wait_finish);
> --
> 2.26.2
>
--
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
next prev parent reply other threads:[~2021-10-28 20:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-28 10:59 [PATCH] xen/balloon: add late_initcall_sync() for initial ballooning done Juergen Gross
2021-10-28 18:13 ` Boris Ostrovsky
2021-10-28 20:16 ` Marek Marczykowski-Górecki [this message]
2021-10-29 4:48 ` Juergen Gross
2021-10-29 9:57 ` Marek Marczykowski-Górecki
2021-10-29 10:22 ` Juergen Gross
2021-10-29 10:32 ` Marek Marczykowski-Górecki
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YXsFO2TMRiJTQM2q@mail-itl \
--to=marmarek@invisiblethingslab.com \
--cc=boris.ostrovsky@oracle.com \
--cc=jgross@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=sstabellini@kernel.org \
--cc=stable@vger.kernel.org \
--cc=xen-devel@lists.xenproject.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).