Re: [BUG REPORT] soft_reset (kexec/kdump) does not work with mainline xen

[Dongli Zhang <dongli.zhang@xxxxxxxxxx>]

Hi Jan,

On 2/24/22 11:15 PM, Jan Beulich wrote:
> On 24.02.2022 23:27, Dongli Zhang wrote:
>> Hello,
>>
>> This is to report that the soft_reset (kexec/kdump) has not been working for 
>> me
>> since long time ago.
>>
>> I have tested again with the most recent mainline xen and the most recent
>> mainline kernel.
>>
>> While it works with my old xen version, it does not work with mainline xen.
>>
>>
>> This is the log of my HVM guest.
>>
>> Waiting for domain test-vm (domid 1) to die [pid 1265]
>> Domain 1 has shut down, reason code 5 0x5
>> Action for shutdown reason code 5 is soft-reset
>> Done. Rebooting now
>> xc: error: Failed to set d1's policy (err leaf 0xffffffff, subleaf 
>> 0xffffffff, msr 0xffffffff) (17 = File exists): Internal error
> 
> I don't suppose you tried you track down the origin of this EEXIST? I think
> it's pretty obvious, as in the handling of XEN_DOMCTL_set_cpu_policy we have
> 
>         if ( d->creation_finished )
>             ret = -EEXIST; /* No changing once the domain is running. */
> 
> Question is how to address it: One approach could be to clear
> d->creation_finished in domain_soft_reset(). But I think it would be more
> clean if the tool stack avoided trying to set the CPUID policy (again) on
> the guest when it soft-resets, as it's still the same guest after all.
> Cc-ing Andrew and Anthony for possible thoughts.
> 

The soft_reset on HVM is successful after I reset d->creation_finished at the
beginning of domain_soft_reset(). So far I am able to use this as workaround to
test kexec/kdump.

However, while my image's console works well on old xen versions, the console on
mainline xen version does not work well.

I connect to the console with "xl console <domid>" immediately after the domU is
panic (and kdump is triggered). I am not able to have the syslogs of kdump
kernel on mainline xen. The same image works on old xen version.

Thank you very much!

Dongli Zhang