running xen on current

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

I have tried and failed to run xen on 3 -current/amd64 systems with
3 different failure modes:

1) laptop:  xen.gz Building a PV Dom0 / ELF: not an ELF binary -> panic/reboot
2) desktop: XEN3_DOM0 panics including PR port-xen/55978
3) server:  Trampoline space cannot be allocated; will try fallback -> reboot

They are all working NetBSD-current/amd64 systems.

My conclusion was that xen is hopelessly broken, so was quite surprised
by Greg Wood's thread about the finer points of running a guest OS, given
that those systems won't even start the host OS.

I dug out an old desktop, and to my pleasant surprise it booted XEN3_DOM0,
and I have managed to run some XEN3_DOMUs.

The difference between the working/broken setups seems to be that the
working one is "BIOS" booting rather than EFI booting.

Among all your xen success stories, are any of you EFI booting?


Cheers,

Patrick


=========================================================================

Some extra gory details

1) laptop:

**** Building a PV Dom0 ****
ELF: Not an ELF binary

***********************************
Panic on CPU 0:
Could not set up DOM0 guest OS
***********************************

Reboot in five seconds...


2) desktop: selection of panics in addition to PR port-xen/55978


[  80.9899999] panic: LIST_INSERT_HEAD 0xffffa080073eec28 ../../../../arch/x86/x86/pmap.c:2285
[  80.9899999] cpu13: Begin traceback...
[  80.9899999] vpanic() at netbsd:vpanic+0x14a
[  80.9899999] snprintf() at netbsd:snprintf
[  80.9899999] pmap_enter_ma() at netbsd:pmap_enter_ma+0x14e7
[  80.9899999] pmap_enter() at netbsd:pmap_enter+0x32
[  80.9899999] udv_fault() at netbsd:udv_fault+0x100
[  80.9899999] uvm_fault_internal() at netbsd:uvm_fault_internal+0x574
[  80.9899999] trap() at netbsd:trap+0x432
[  80.9899999] --- trap (number 6) ---
[  80.9899999] 7a60617787af:
[  80.9899999] cpu13: End traceback...

[  75.6599981] panic: kernel diagnostic assertion "ncp->nc_dvp == dvp" failed: file "../../../../kern/vfs_cache.c", line 432 
[  75.6599981] cpu0: Begin traceback...
[  75.6599981] vpanic() at netbsd:vpanic+0x14a
[  75.6599981] kern_assert() at netbsd:kern_assert+0x48
[  75.6599981] cache_lookup_entry() at netbsd:cache_lookup_entry+0xde
[  75.6599981] cache_lookup_linked() at netbsd:cache_lookup_linked+0x160
[  75.6599981] namei_tryemulroot() at netbsd:namei_tryemulroot+0x298
[  75.6599981] namei() at netbsd:namei+0x29
[  75.6599981] vn_open() at netbsd:vn_open+0x8f
[  75.6599981] do_open() at netbsd:do_open+0x119
[  75.6599981] do_sys_openat() at netbsd:do_sys_openat+0x74
[  75.6599981] sys_open() at netbsd:sys_open+0x24
[  75.6599981] syscall() at netbsd:syscall+0x9c
[  75.6599981] --- syscall (number 5) ---
[  75.6599981] netbsd:syscall+0x9c:
[  75.6599981] cpu0: End traceback...


3) server: EFI boot of Feb 6 2021, xenkernel413-4.13.3.tgz, serial console

On serial console, all that is seen is:

2415648+1324000=0x3910ec         
Loading /var/db/entropy-file
Loading /netbsd-XEN3_DOM0
Start @ 0xce600000 [1=0xce991000-0xce9910ec]... 
Trampoline space cannot be allocated; will try fallback.

then it reboots