[Fedora-xen] Fedora 7 kernels

[Jason Solan]

Thank you for the detailed and full explanation.
I appreciate all the work the Fedora and Red Hat teams have done with
the XEN development.

I was just very surprised(and frustrated) that a fully virtualized F7
would not work.  We have implemented a couple of small domU's
(webservers,ntp,etc) on a RHEL 5 32-bit dom0.  We were looking for a way
to move the vm's to some of our more powerful 64-bit machines.  Some of
the domU's where FC6 and they worked perfectly in HVM mode.  Others were
F7 and we were unable to do anything with them.

Looking forward to trying out the newer kernels (as well as the RHEL 5.1
release).

Again, thanks for the information, its nice to see it all very clearly
explained out in one place.


On Thu, 2007-09-27 at 05:22 +0100, Daniel P. Berrange wrote:
> On Tue, Sep 25, 2007 at 04:17:24PM -0400, Jason Solan wrote:
> > I've had a lot of problems with Fedora 7 and XEN and I've read some
> > messages on this mailing list indicating the F7 kernel is more or less
> > broke with xen.
> > By problems I mean that 32 bit guests on 64 bit dom0 does not work at
> > all for me.  Neither paravirtualized (as was a main feature of xen 3.1)
> > or fully virtualized.
> 
> The release notes associated with Xen 3.1 turned out to be not quite
> accurate on the subject of 32-on-64 & we didn't realize this when we
> made corresponding release notes for Fedora 7. 
> 
> Xen 3.1 lets you run a 32-bit DomU kernel on a 64-bit hypervisor + Dom0
> *ONLY IF* the DomU kernel was also based on Xen 3.1.  ie, a 32-bit DomU
> kernel based on older Xen 3.0.* release would will not work on Xen 3.1
> Unfortunately all the Fedora kernels for FC6 are 3.0.3 and  F7 GA was 
> based on Xen 3.0.4, so neither will work on a Xen 3.1 hypervisor + Dom0.
> 
> In the current Xen-unstable upstream (which will become Xen 3.2) there
> is now back-compat support for running older DomU kernels. In the most
> recent update of Xen in  F-7 updates-testing we have included a handful
> of backports which at least let us boot a 32-bit FC6 and F7  domU installer
> kernel on a 64-bit F7 / F8 host.  
> 
> There are ongoing fixes in upstream Xen for various stability issues
> when running 32-on-64 though, so it is not perfect. You may be lucky 
> with our latest updates and have it work, but equally you may not be
> lucky. We're tracking upstream & will pull in fixes when available.
> 
> > Combinations I've tried:
> > F7 x86_64 dom0 -> F7 x86 domU PV
> 
> Works in basic testing. Has stability problems.
> 
> > F7 x86_64 dom0 -> F7 x86 domU HVM
> 
> F7 HVM has been broken since GA for reasons unrelated to the 32-on-64
> stuff. A last minute clock-source & bootloader change screwed things
> up. Yesterday we pushed newer kernel-xen and xen RPMs to updates-testing
> which hopefully make this work.
> 
> > RHEL 5 x86_64 dom0 -> F7 x86 domU HVM
> 
> Not going to work - missing the fix I mention above.
> 
> > RHEL 5.1 Beta x86_64 dom0 -> F7 x86 domU PV
> 
> Works for me, at least to boot the installer. There are sometimes some
> stability issues though, since Xen 3.1 was far from complete in its
> 32-on-64 support.
> 
> > RHEL 5.1 Beta x86_64 dom0 -> F7 x86 domU HVM
> 
> Not going to work - missing the fix I mention above.
> 
> > RHEL 5 x86 dom0 -> F7 x86 domU PV  -- Only one that works (32 on 32 PV)
> 
> Matched 32-on-32 and 64-on-64  kernels have always worked. 
> 
> > I had read a while ago (June?) that a kernel update would be coming soon
> > to fix the 32 on 64 PV issue, however I've ran in several new kernels
> > and none seem to fix the issue.
> > https://www.redhat.com/archives/fedora-xen/2007-June/msg00031.html
> 
> The fix required both kernel-xen & xen updates which are finally available
> in updates-testing.
> 
> > I've also repeatedly tried to run a 32 bit HVM fedora 7 guest on 64 bit
> > machines and had that fail similar to this:
> 
> F7  HVM guests have known issues, also hopefully now fixed.
> 
> > http://www.redhat.com/archives/fedora-xen/2007-June/msg00094.html
> > 
> > Is there any more work planned for Fedora 7 and xen, or should I just
> > wait until F8?  Or am I just doing something wrong and the problems I'm
> > having should be working on the current builds?
> 
> 
> Fedora 7 will continue to have updates until its end-of-life. The issue
> is that even in upstream Xen 32-on-64 doesn't have the same level of 
> stability as 32-on-32, or 64-on-64.
> 
> Dan.




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