Xen MP panics in cpu_switchto()

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hello,
A current Xen domU kernel fails to boot with:
[   1.0000000] hypervisor0 at mainbus0: Xen version 4.11.3nb1
[   1.0000000] vcpu0 at hypervisor0
[   1.0000000] vcpu0: Intel(R) Xeon(TM) CPU 3.00GHz, id 0xf64
[   1.0000000] vcpu0: node 0, package 0, core 1, smt 1
[   1.0000000] vcpu1 at hypervisor0
[   1.0000000] vcpu1: Intel(R) Xeon(TM) CPU 3.00GHz, id 0xf64
[   1.0000000] vcpu1: node 0, package 1, core 0, smt 0
[   1.0000000] xenbus0 at hypervisor0: Xen Virtual Bus Interface
[   1.0000000] xencons0 at hypervisor0: Xen Virtual Console Driver
[   1.9901295] uvm_fault(0xffffffff80d5c120, 0x0, 1) -> e
[   1.9901295] fatal page fault in supervisor mode
[   1.9901295] trap type 6 code 0 rip 0xffffffff8020209f cs 0x8 rflags 0x10246 cr2 0x28 ilevel 0 rsp 0xffffb7802b19de88
[   1.9901295] curlwp 0xffffb7800083b500 pid 0.15 lowest kstack 0xffffb7802b1992c0
kernel: page fault trap, code=0
Stopped in pid 0.15 (system) at netbsd:cpu_switchto+0xf:        movq    28(%r13),%rax
cpu_switchto() at netbsd:cpu_switchto+0xf

both amd64 and i386. A boot with vcpus=1 succeeds, so I guess something is
missing in initialisations of secondary CPUs.
This happens with the 202001101800Z but the problem is probably older than
that (the testbed used vcpus=1 until today)

Any idea ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
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