Hello,
Am Dienstag 24 August 2010 14:12:24 schrieb Daniel P. Berrange:
> If you can provide the 'xm' config file, the libvirt XML and the output
> of 'xm list --list $GUESTNAME' when the guest is succesfully running we
> can add a test case to validate this PAE setup & fix the xen driver.
I attached 8 files:
1. xen-fv-w2k8.broken.xml is my initial file, which was used with 'virsh
define' + 'virsh start'.
2. xen-fv-w2k8.broken.xm was created using "virsh domxml-to-native xen-xm"
3. xen-fv-w2k8.broken.dump was created using "xm list --long Windows2008r2_64"
4. xen-fv-w2k8.fixed.xml with just '<pae/>' added, 'virsh define' + 'virsh
start'.
5.-6. xen-fv-w2k8.fixed.{xm,dump} analog to above.
7. xen-fv-w2k8.clean.xm is without the pae=[01] line, so 'xm create' uses it's
default.
8. xen-fv-w2k8.clean.dump of 'xm list --long' after 'xm create'
501 root@xen1=xen64:~ 0# xm info
host : xen1
release : 2.6.32-ucs11-xen-amd64
version : #1 SMP Sat Jul 31 07:49:13 UTC 2010
machine : x86_64
hw_caps :
078bf3ff:ebd3fbff:00000000:00000010:00002001:0000001d:0000001d:00000000
virt_caps : hvm
xen_major : 3
xen_minor : 4
xen_extra : .3
xen_caps : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32
hvm-3.0-x86_32p hvm-3.0-x86_64
> In 64-bit Xen, the pae flag indicates whether the CPU exposed supports
> long mode. So if you don't set the PAE flag on 64-bit Xen, you get a
> 32-bit PAE guest. If you do set the PAE flag, you get a 64-bit guest.
> Yes, you read that right, not setting PAE, gets you a PAE enabled guest
> just with 32 instead of 64 bits :-)
>
> In terms of the domain XML design, the choice between 32 and 64 bits is
> intended to be done based on the arch field:
>
> <os>
> <type arch='x86_64'...
> ...
> </os>
That is what I expected as well: neither for Windows 2k8 nor for Linux would I
get a 64 bit guest. Only after adding the <pae/> feature it worked.
Perhaps related: Setting "arch=x86_64" for Xen domains never made a difference
for me: On the next "virsh dumpxml" that attribute was gone again making it
impossible to distinguish between 32 and 64 bit Xen domains.
> The pae flag in domain XML should be reflecting whether pae is enabled
> in the guest.
If I understand pae right, x86_64 used a page-table-layout very similar to
x86_32+pae, which makes doing the Virtual Memory mapping between host and
guests easy. For x86_32 without pae you'd need to do some heavy reshuffling,
because the page tables would be totally different.
I noticed the pae problem during my testing: guests started via "xm
create/start" ran fast, while guestss started via "virsh start" were very
slow. As soon as one non-pae-guest was running, the whole system got
unresponsive. It seemed to be related to the memory size, since running a
guest with 128M or 512M made a huge difference.
> The capabilities XML should be reporting whether the guest ABI includes
> the PAE flag or not. So I think the 32bit capabilities shouldn't have
> included <nonpae/> there, and perhaps 64-bit should have had <pae/>.
> Ultimately though I think our mistake is in passing the <pae> flag from
> the domain XML, straight through to the hypervisor. I'm rather wary of
> changing this, because of the risk of regressions, but if you can supply
> the 3 files I asked for above, we can investigate whether its feasible
The missing <pae/> is translated to pae=0, which overwrites Xens default.
Because of that my code currently tests for xen on x86_64 and than always
adds <pae/> to make it work. My expectation would be that the capabilities
XML should thus report <pae/>, if an application is supposed to add the
<pae/> feature to get an 64 bit xen-fv domain.
Sincerely
Philipp
--
Philipp Hahn Open Source Software Engineer hahn@xxxxxxxxxxxxx
Univention GmbH Linux for Your Business fon: +49 421 22 232- 0
Mary-Somerville-Str.1 28359 Bremen fax: +49 421 22 232-99
http://www.univention.de
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(domain
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<domain type='xen'>
<name>Windows2008r2_64</name>
<memory>524288</memory>
<vcpu>1</vcpu>
<os>
<type arch='x86_64' machine='xenfv'>hvm</type>
<loader>/usr/lib/xen/boot/hvmloader</loader>
<boot dev='cdrom'/>
</os>
<features>
<acpi/>
<apic/>
<!--pae/-->
</features>
<devices>
<emulator>/usr/lib/xen/bin/qemu-dm</emulator>
<disk type='file' device='cdrom'>
<driver name='file'/>
<source file='/mnt/omar/vmwares/iso-images/windows/server/windows2008-server-R2_x64.iso'/>
<target dev='hdc' bus='ide'/>
<readonly/>
</disk>
<input type='mouse' bus='ps2'/>
<graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0' keymap='de'/>
</devices>
</domain>
name = "Windows2008r2_64" uuid = "7d9dd677-8e0f-d6d9-361a-743731926b01" maxmem = 512 memory = 512 vcpus = 1 builder = "hvm" kernel = "/usr/lib/xen/boot/hvmloader" boot = "d" pae = 1 acpi = 1 apic = 1 localtime = 0 on_poweroff = "destroy" on_reboot = "restart" on_crash = "destroy" device_model = "/usr/lib/xen/bin/qemu-dm" vfb = [ "type=vnc,vncunused=1,vnclisten=0.0.0.0,keymap=de" ] disk = [ "file:/mnt/omar/vmwares/iso-images/windows/server/windows2008-server-R2_x64.iso,hdc:cdrom,r" ] parallel = "none" serial = "none"
name = "Windows2008r2_64" uuid = "29b2279b-e48d-dcfa-7f56-05f98ba67e03" maxmem = 512 memory = 512 vcpus = 1 builder = "hvm" kernel = "/usr/lib/xen/boot/hvmloader" boot = "d" pae = 0 acpi = 1 apic = 1 localtime = 0 on_poweroff = "destroy" on_reboot = "restart" on_crash = "destroy" device_model = "/usr/lib/xen/bin/qemu-dm" vfb = [ "type=vnc,vncunused=1,vnclisten=0.0.0.0,keymap=de" ] disk = [ "file:/mnt/omar/vmwares/iso-images/windows/server/windows2008-server-R2_x64.iso,hdc:cdrom,r" ] parallel = "none" serial = "none"
(domain
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<domain type='xen'>
<name>Windows2008r2_64</name>
<memory>524288</memory>
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<os>
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<boot dev='cdrom'/>
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<features>
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<readonly/>
</disk>
<input type='mouse' bus='ps2'/>
<graphics type='vnc' port='-1' autoport='yes' listen='0.0.0.0' keymap='de'/>
</devices>
</domain>
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name = "Windows2008r2_64" uuid = "29b2279b-e48d-dcfa-7f56-05f98ba67e03" maxmem = 512 memory = 512 vcpus = 1 builder = "hvm" kernel = "/usr/lib/xen/boot/hvmloader" boot = "d" acpi = 1 apic = 1 localtime = 0 on_poweroff = "destroy" on_reboot = "restart" on_crash = "destroy" device_model = "/usr/lib/xen/bin/qemu-dm" vfb = [ "type=vnc,vncunused=1,vnclisten=0.0.0.0,keymap=de" ] disk = [ "file:/mnt/omar/vmwares/iso-images/windows/server/windows2008-server-R2_x64.iso,hdc:cdrom,r" ] parallel = "none" serial = "none"
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