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Re: [Xen-users] [Xen-devel] Cannot Start Linux Paravirtualized (PV) Guests with Xen 4.2-unstable

> 3) When I was installing Ubuntu 12.04 Beta 1 Precise Pangolin amd64 as
> a HVM domU in either Xen 4.1.3-rc1-pre or Xen 4.2-unstable, it hanged
> at COPYING FILES during installation. Hence I have to abort the HVM
> domU installation. Disk I/O performance is very poor.
> 4) Disk I/O performance is very poor with Debian 6.0 Squeeze PV domU
> in Xen 4.2-unstable and with Fedora 16 x86-64 PV domU in Xen
> 4.1.3-rc1-pre. The mouse cursor movement in both Fedora 16 and Debian
> 6.0 Squeeze PV domU is very sluggish and unresponsive. It also takes a
> long time to format filesystems and install packages in PV domU during
> OS installation. What causes the performance penalty in disk I/O?
> 5) Disk I/O performance is also very poor with Ubuntu 12.04 Beta 1 HVM
> domU installation. Formatting filesystems and copying files during
> installation take a long time. Mouse cursor movement is also very
> unresponsive.

I installed Ubuntu 12.04 beta server (AMD 64) and xen hypervisor from
ubuntu xen packages (v4.1). 
Then I installed Ubuntu 10.04 server as PV DomU and Ubuntu 10.04 desktop
as HVM DomU.
I could not enable IO virtualization, because iommu=1 and iommu=verbose
parameters seem to be not working.

When I run tests for my specific software I found, that in Ubuntu 10.04
HVM DomU there are too many interrupts when dealing with network.
Processor took about 50%si. I did not test disk IO, but think the
picture should be the same.

But I found solution, which works perfect for me. I installed Ubuntu
12.04 desktop beta (i386) as PVHVM DomU. It installed without hangs and
it works very fast with network and disk. 

Only one thing looks ugly: I can't change maximal resolution of the
desktop more than 1024x768 (despite of settings stdvga=1 and

Also, I would like to know, how to enable verbose logs for iommu,
because xm dmesg does not show me any information about VT-d. I have the
(XEN) Command line: placeholder iommu=verbose
in the dmesg logs, but still not got verbose logs...

Sergey Zhukov 

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