Re: Regression between Xen 4.6.0 and 4.7.0, Direct kernel boot on a qemu-xen and seabios HVM guest doesn't work anymore.

[Wei Liu <wei.liu2@citrix.com>]

On Mon, Oct 17, 2016 at 05:28:17PM +0200, Sander Eikelenboom wrote:
> Thursday, October 13, 2016, 4:43:31 PM, you wrote:
> 
> > Hi Jan / Wei,
> 
> > Took a while before i had the chance to fiddle some more to find the actual culprit.
> > After analyzing the output of xl -vvvvv create somewhat more i came to the 
> > insight it was probably Qemu and not Xen causing the fault.
> 
> > As a test I just used a qemu-xen binary build with xen-4.6.0 booting up a guest with
> > direct kernel boot mode on xen-unstable. And that old qemu binary works fine.
> 
> > After testing i can conclude, Jan was right, the bisection was a red herring,
> > the problem is caused by some change in Qemu and not by something in the Xen tree.
> > (strange thing is that for as far as i know i did a "make distclean" between 
> > every build (taking a lot of time), which should have pulled a fresh qemu-xen 
> > tree and therefor the bisection should have lead to a commit with a Config.mk 
> > hash change for qemu-xen version.)
> 
> > Will see if i can find some more time and bisect qemu and find the culprit.
> 
> > --
> > Sander
> 
> 
> Unfortunately i have to give up on this issue, for me it's impossible to bisect this 
> issue with my present git-foo.
> 
> The first try with bisection of the whole xen-tree seems to have hit the issue that the 
> qemu-revision that gets pulled on a fresh build is "master" during the whole
> dev period. That creates havoc when trying to bisect, since you are testing 
> combinations that were never developed (nor auto tested) in that combination
> (especially when a xen-tree and qemu-tree change have a dependency like Roger's 
> "xen: fix usage of xc_domain_create in domain builder")
> 
> While trying to bisect only qemu (keeping xen itself on RELEASE-4.6.0 and 
> seabios on rel-1.8.2) it get stuck on issues with that tree.
> Between 4.6.0 and 4.7.0 the qemu tree switched from git://xenbits.xen.org/qemu-upstream-4.6-testing.git
> to git://xenbits.xen.org/qemu-xen.git),after that there seem to have 
> been a lot of merges going back and forth and to me it seems a mess (but as i 
> said it could also be a lack of git-foo). I tried by manual bisecting, removing 
> and cloning trees again etc. but that doesn't suffice, it's all going no-where.
> (while the known good build (plain RELEASE-4.6.0) always works, so it doesn't 
> seem to be some random problem)
> 

Thanks for trying.

> So perhaps some dev can at least verify that the issue is there (since 4.7.0)
> and put it on the "known broken" list of things.
> 

I will put this into the list of things I need to look at.

Wei.

> --
> Sander
> 

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