Re: [Xen-devel] Latest development (master) Xen fails to boot on HP ProLiant DL20 GEN10

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.09.2019 00:31, Roman Shaposhnik wrote:
> Jan, Roger, thank you so much for the initial ideas. I tried a few of
> those and here's where I am.
> 
> First of all, it is definitely related to CPU bring up. Adding
> cpuidle=0 to xen command line made Xen boot.
> 
> Then, a good friend of mine (who you may know from ancient Xen days
> ;-)) suggested that this could be related to this:
>      https://wiki.xenproject.org/wiki/Xen_power_management
> so I went to the BIOS settings and quite to my surprise all of them
> were grayed out (not tweakable).
> 
> The only one that wasn't was 2xAPIC support. So just for kicks -- I
> disabled that.
> 
> That, in turn, made Xen boot even without cpuidle=0. I'm attaching that log.

Interesting, but unfortunately this particular log is of no real use
for investigation of the issue (other than knowing the CPU model). I
also notice it's a 4.12.0 log, when your original report was against
latest master.

> So I guess at this point, you could say that I have a functional
> system, but I'm curious whether you guys would be interested to look
> into 2xAPIC situation.

Of course we do. As a next step I'd suggest reverting the BIOS settings
change you did, and instead using the "x2apic=0" Xen command line option.

And then we of course need a complete boot log (as requested earlier) of
a problem case.

Further I'd suggest moving away from the black-and-white "cpuidle="
option, and instead limiting use of deep C states ("max_cstate="). I
wouldn't be surprised if this was the issue; we'd then have to first
of all go through errata for the part your system is using.

Jan

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