Re: Stable/13 doesn't boot with xen

On Tue, Jun 07, 2022 at 12:19:01PM -0700, Brian Buhrow wrote:
> 	hello Roger.  I'm happy to do what I can, but it is difficult to get a lot of time to
> bring this server down to get diagnostic data.  Having said that, I'm happy to look at the code
> via bisection if you can help me by providing sample commands to git to assist me in getting
> the idea.  I'm pretty new to git and am still learning my way around it.

`git bisect` [0] will simply point to commits that you build and then tell
git whether the code work or not, it's basically a binary search over
a range of commits to find the commit that introduced the issue.

For example in this case you would use, from a src.git checkout:

$ git fetch
$ git bisect start 0bbbd845fd32ef07707c03d1dc4e4b27f6ebef83 fc952ac2212b121aa6eefc273f5960ec3e0a466d
$ make -j8 kernel
$ reboot
<... test whether the kernel boots ...>
$ git bisect [bad|good]

Select either bad or good from the command above depending on whether
the proposed commit works.  Git will then propose a new commit for you
to test until it can pin the commit that introduced the regression.

If a commit fails to build you can also use `git bisect skip` to
select a different commit for test.

> Another question which you may or may not know the answer to.  Since the server in question
> runs FreeBSD fine when it's running on bare metal, do you think the bad commit would be xen
> specific or do you think it's some change related to the difference in the way the hardware
> looks to FreeBSD when it's looking at it through xen versus looking at the bare machine?

I don't think there have been any? Xen related changes to stable/13
since 13.1 was branched, so it's unlikely to be a Xen specific commit
I would think.

It's also weird that HEAD works for you, which means it's likely
either a commit that changed when backported to stable-13, or a commit
that had some prerequisites to work correctly on Xen, and those
prerequisites haven't been backported to stable-13.

Thanks, Roger.

[0] https://git-scm.com/docs/git-bisect