Re: Problems with APIC on versions 4.9 and later (4.8 works)

[Claudemir Todo Bom <claudemir@xxxxxxxxxxx>]

Em qua., 20 de jan. de 2021 às 12:13, Jürgen Groß <jgross@xxxxxxxx> escreveu:
>
> On 20.01.21 09:50, Jan Beulich wrote:
> > On 19.01.2021 20:36, Claudemir Todo Bom wrote:
> >> I do not have serial output on this setup, so I recorded a video with
> >> boot_delay=50 in order to be able to get all the kernel messages:
> >> https://youtu.be/y95h6vqoF7Y
> >
> > This doesn't show any badness afaics.
> >
> >> This is running 4.14 from debian bullseye (testing).
> >>
> >> I'm also attaching the dmesg output when booting xen 4.8 with  the same
> >> kernel version and same parameters.
> >>
> >> I visually compared all the messages, and the only thing I noticed was that
> >> 4.14 used tsc as clocksource and 4.8 used xen. I tried to boot the kernel
> >> with "clocksource=xen" and the problem is happening with that also.
> >
> > There's some confusion here I suppose: The clock source you talk
> > about is the kernel's, not Xen's. I didn't think this would
> > change for the same kernel version with different Xen underneath,
> > but the Linux maintainers of the Xen code there may know better.
> > Cc-ing them.
>
> This might depend on CPUID bits given to dom0 by Xen, e.g. regarding
> TSC stability.
>

Looks like the CPUID changes I observed and wrote on the other
messages are another
problem I may end up with. I narrowed down the cause of the problem on
booting of dom0 with more than 1 core on the following commit:

https://github.com/xen-project/xen/commit/63e1d01b8fd948b3e0fa3beea494e407668aa43b

Code built from this commit doesn't boot, built from the parent of it, boots.

Now, there is something I can do on the command line to make it boots?
Or its needed to fix on the code?

Best regards,
Claudemir