Re: [Xen-devel] 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.

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

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)

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.

--
Sander


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel