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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 24.09.2019 20:20, Roman Shaposhnik wrote:
> I'm a bit at a loss of what's happening here, but it seems that
> the latest Xen from master fails to boot on HP ProLiant DL20
> GEN10 server (same Xen boots fine on every other piece of
> hardware in my lab).

First of all - is this known to be a regression, i.e. is older
Xen known to work on this particular hardware?

> There are absolutely no signs of what's going wrong with it.
> It just stops at
> 
> (XEN) HVM: ASIDs enabled.
> (XEN) HVM: VMX enabled
> (XEN) HVM: Hardware Assisted Paging (HAP) detected
> (XEN) HVM: HAP page sizes: 4kb, 2MB, 1GB
> ...
> (XEN) Adding cpu 1 to runqueue 0
> (XEN) mwait-idle: max C-state count of 8 reached
> (XEN) Adding cpu 2 to runqueue 0
> (XEN) mwait-idle: max C-state count of 8 reached
> 
> I guess the only clue is that your typical line of:
> 
> (XEN) Brought up X CPUs
> 
> never gets printed -- so perhaps there's something wonky
> going on with CPU initialization.
> 
> Any advice on how to diagnose this further will be greatly appreciated.

Second, as always, a complete log will already help, e.g. by allowing
us to see what CPU model it is that's in the system. Iirc there was a
similar report for a certain Atom variant, but I assume it's a Skylake
here. Maximum verbosity (loglvl=all) and extra CPU related output
("cpuinfo") should be enabled for this.

Furthermore, while I don't think the (bogus; I'll make a patch in a
minute) mwait-idle message is related, excluding there to be an effect
would be a helpful extra data point ("cpuidle=0" for simplicity).

Another potentially useful experiment would be to limit the number of
CPUs to boot ("nosmp" should boot fine in any case, so "maxcpus="
would be what you'd want to play with), and to override the default
of whether to park secondary hyperthreads ("smt=0" and "smt=1").

Jan

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