Re: [Xen-devel] repeating 'd1v0 Over-allocation for domain 1' messages in xen 4.7 Host logs on PVHVM Guest launch

[PGNet Dev <pgnet.dev@xxxxxxxxx>]

Reading @

 How to know if the balloon driver is running
  http://www.gossamer-threads.com/lists/xen/users/315064#315064

        "...
        IIRC the core balloon driver is always present when Xen is enabled and
        so the kernel will respond to requests from the host/toolstack to change
        the amount of RAM (e.g "xm/xl mem-set foo" in dom0, which would result
        in changes to /proc/meminfo).

        In order to get in-guest access to control ballooning you need to
        CONFIG_XEN_BALLOON enable and load the xen-balloon.ko module. I'm not
        sure but I think with modern kernels this will appear in /sys and
        not /proc.
        ...
        AFAIK the balloon driver is started if you just have CONFIG_XEN.

	LIke I said before CONFIG_XEN_BALLOON enables additional support for 
controlling the balloon driver from within the guest (as opposed to from 
the host toolstack).
        ..."

in the Guest,

        grep -i config_xen= /boot/*config*
                /boot/config-4.4.0-28-generic:CONFIG_XEN=y
        grep -i xen /boot/*config* | grep -i balloon
> >                 /boot/config-4.4.0-28-generic:CONFIG_XEN_BALLOON=y
                /boot/config-4.4.0-28-generic:CONFIG_XEN_SELFBALLOONING=y
                
/boot/config-4.4.0-28-generic:CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y
                
/boot/config-4.4.0-28-generic:CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT=512

        find /sys /proc -type d | grep -i balloon | grep xen
                /sys/devices/system/xen_memory/xen_memory0/selfballoon
                /proc/sys/xen/balloon

        ls -al /proc/sys/xen/balloon
                hotplug_unpopulated

How do you blacklist the Guest ballooning?

Perhaps related?  Not clear 2 me that it's the same issue,

 xen/balloon: cancel ballooning if adding new memory failed

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3dcf63677d4eb7fdfc13290c8558c301d2588fe8

There's also balloon-related comments at

 http://wiki.xenproject.org/wiki/XenParavirtOps

although they now look somewhat out of date w.r.t. current 4x kernel

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