From 3ee35f6f110e2258ec94f0d1397fac8c26b41761 Mon Sep 17 00:00:00 2001 From: Juergen Gross To: linux-kernel@xxxxxxxxxxxxxxx Cc: Boris Ostrovsky Cc: Juergen Gross Cc: Stefano Stabellini Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx Date: Thu, 21 Oct 2021 12:51:06 +0200 Subject: [PATCH] xen/balloon: add late_initcall_sync() for initial ballooning done MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. Reported-by: Marek Marczykowski-Górecki Signed-off-by: Juergen Gross --- 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