Re: [Xen-devel] Cannot start up HVM guest when maxmem is not equal to memory and HAP is enabled.

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Thu, Jan 12, 2012 at 9:15 AM, Yufang Zhang <yufang521247@xxxxxxxxx> wrote:
> Actually, you would be exposed to this problem whenever you restart xend and
> then reboot the hvm guest, even you set  maxmem == memory in the config file
> of that guest. When xend is restarted, it tries to recreate guest
> information. memory_dynamic_max and memory_static_max, which are used
> to calculate memory and maxmem, are re-calculated from mem_kb and maxmem_kb
> respectively.  mem_kb is not equal to maxmem_kb. Thus memory != maxmem after
> xend restarts, and rebooting this hvm guest later would leads guest
> crash/hang.

Ah, interesting.  Yeah, that is certainly a bug -- not sure whom to
contact about fixing that.  Keith?

> I check the xend code of xen-unstable,  the related logic didn't change
> since xen-3.4. So I *guess* a hvm guest without balloon driver would crash
> after some time(when it dirties enough memory) after you restarting xend and
> rebooting the guest on xen-4.1.

Should a user be changing the "memory" setting without having a
balloon driver active?  If the balloon driver *is* active, we'd want
that setting to be preserved across reboot.  Does xend know if there
is an active balloon driver?  If not, I think we just have to leave it
as it is.

 -George

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