Xen users - Feb 2013 - Problem using PoD on Xen 4.2.1 (win domU crash)

Hi,

In short:
Windows domU doesn't show any ballooned memory and finally crashes
("out of PoD memory") when "starting ballooned".

We tested on 2 different hosts and windows guests:
  Windows Server 2008 R2 and 2003.
  Xen 4.2.1 on gentoo, dom0 kernels: 3.7.x
  signed gplpv drivers from univention.

When configured to start ballooned (eg. mem=1GB, max=4GB)
we see the following behaviour:

- "xl list" says, the guest uses 1GB of memory
- windows shows 4GB physical memory (as expected)
- but windows shows no sign of a balloon (ie: all 4GB is free)
- we are able to eat all the 4GB without paging.
- "xl list" doesn't notice any changes (always stays at 1GB).
- If we try to allocate above physical memory of the host, the domU just
crashes:
  (XEN) p2m_pod_demand_populate: Dom3 out of PoD memory! (tot=131064
ents=1965536 dom3)
  (XEN) domain_crash called from p2m-pod.c:1077

We didn't start ballooned windows domUs before, so we're not exactly
sure on how it should behave (expected to see the "ballooned region"
right after booting windows; and certainly no crashes :-)).

Is this a bug in this special combination of components, or did we mess up with
our configuration?

domU Config:
------------------------------
builder = "hvm"
name = "win2008"
viridian = 1
memory = 1024
maxmem = 4096
vcpus = 2
vif = [ 'bridge=xenbr0, mac=00:18:4e:fa:ab:13, model=e1000'  ]
disk = [ 'phy:/dev/sda3,hda,rw' ]
vnc =1
vnclisten="127.0.0.1"
vncpasswd="test"
stdvga = 1
videoram = 8 
acpi = 1
apic = 1
usb = 1
usbdevice = "tablet"
serial='pty'
xen_platform_pci=1
------------------------------

yours,
- peter


-- 
Peter Gansterer

PARADIGMA Unternehmensberatung GmbH
Mariahilferstraße 47/1/3
A-1060 Wien
Tel: 0043-(0)1-585 49 72
http://www.paradigma.net

Firmenbuchnummer: FN 134564 p
Rechtsform: GmbH
Firmenbuchgericht: Handelsgericht Wien

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> In short:
> Windows domU doesn''t show any ballooned memory and finally crashes
> ("out of PoD memory") when "starting ballooned".
> 
> We tested on 2 different hosts and windows guests:
>   Windows Server 2008 R2 and 2003.
>   Xen 4.2.1 on gentoo, dom0 kernels: 3.7.x
>   signed gplpv drivers from univention.
> 
Which version of the univention drivers? Maybe the univention signed drivers are
bit old.

Try one of:
http://www.meadowcourt.org/private/gplpv_2000_0.11.0.372.msi
http://www.meadowcourt.org/private/gplpv_2000_0.11.0.372_debug.msi
http://www.meadowcourt.org/private/gplpv_2003x32_0.11.0.372.msi
http://www.meadowcourt.org/private/gplpv_2003x32_0.11.0.372_debug.msi
http://www.meadowcourt.org/private/gplpv_2003x64_0.11.0.372.msi
http://www.meadowcourt.org/private/gplpv_2003x64_0.11.0.372_debug.msi
http://www.meadowcourt.org/private/gplpv_Vista2008x32_0.11.0.372.msi
http://www.meadowcourt.org/private/gplpv_Vista2008x32_0.11.0.372_debug.msi
http://www.meadowcourt.org/private/gplpv_Vista2008x64_0.11.0.372.msi
http://www.meadowcourt.org/private/gplpv_Vista2008x64_0.11.0.372_debug.msi
http://www.meadowcourt.org/private/gplpv_XP_0.11.0.372.msi
http://www.meadowcourt.org/private/gplpv_XP_0.11.0.372_debug.msi

and give it a go. I just tried it on 2003 and it works fine, or at least from 30
seconds testing it correctly shows that of the 4G I assigned to the domu, only
787MB is free immediately after boot. If it still doesn''t work, use the
_debug version and send me the /var/log/xen/qemu-dm-<domu name>.log. You
should see something like:

13005008537656: XenPCI --> XenPci_InitialBalloonDown
13005008537656: XenPCI     base = 0x40000000, Xen Signature = XenVMMXenVMM, EAX
= 0x40000002
13005008537671: XenPCI     Xen Version 4.1
13005008537671: XenPCI     Hypercall area at 8AD62000
13005008537671: XenPCI     XENMEM_maximum_reservation = 1049600
13005008537671: XenPCI     XENMEM_current_reservation = 263157
13005008537671: XenPCI     Trying to give 3145772 KB (3072 MB) to Xen
13005008556656: XenPCI <-- XenPci_InitialBalloonDown

James

> Hi,
> 
> I just tried on my win2008R2/64 and it is still the same with the new
driver.
> Started with 1/8GB; no sign of a "balloon"; did some
alloc/dealloc until it
> crashed.
> Tried both regular & debug. Log and xl dmesg attached.
> 
> (To make sure, I just also tried with 1/4GB - the same)
> 
Your one says:

13005008825593: XenPCI --> XenPci_InitialBalloonDown
13005008825593: XenPCI     base = 0x40000000, Xen Signature = Microsoft Hv, EAX
= 0x40000006
13005008825593: XenPCI     base = 0x40000100, Xen Signature = XenVMMXenVMM, EAX
= 0x40000102
13005008825593: XenPCI     Xen Version 4.2
13005008825593: XenPCI     Hypercall area at FFFFFA80063A4000
13005008825593: XenPCI     XENMEM_maximum_reservation = 262400
13005008825593: XenPCI     XENMEM_current_reservation = 262136
13005008825609: XenPCI     Trying to give 1056 KB (1 MB) to Xen
13005008825624: XenPCI <-- XenPci_InitialBalloonDown

So for some reason gplpv can''t determine that you want to be ballooned
down 7GB, it''s just giving back the default 1MB (there are/were some
problems with save/restore when this didn''t happen).

I notice you are using 4.2 while I''m using 4.1, which probably accounts
for the difference.

I''ll post on xen-devel to ask what the correct way of determining this
is under 4.2...

I suspect that giving your VM 8G but ballooning down to 1G might be pushing
things a bit. There are overheads with higher amounts of memory, and Windows
will make some assumptions about how large to allocate internal tables etc based
on the amount of memory.

James