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Xen 4.18 doesn't display on an iDRAC-6 console, and NetBSD console=pc locks up early in boot



[[ Resending this without the image attachment.... ]]

So I've got this remote Xen server, a Dell R510, that I manage and I
only have iDRAC-6 access to its "vga" console.

My recent upgrade to 4.18 (from 4.13) revealed some problems:

1. Xen does not display anything on the console.

2. NetBSD XEN3_DOM0 (in this case a somewhat older -current) when
   running under 4.18 locks up early in the boot of the dom0.  (see
   attached image) (same kernel boots find with console=pc under 4.13)

However I found that if I told/allowed NetBSD XEN3_DOM0 to use
xencons(4) then it boots "silently" and quite quickly and all is well,
except of course for anyone expecting to use the actual console for
anything, e.g. single-user mode, is screwed.  Not the end of the world
though if one has a GENERIC kernel also available.  Not that it would
be of any use, but too bad Xen won't allow "xl console Domain-0".

Furthermore the XEN3_DOM0 kernel doesn't see a com0 on this machine with
the current working boot (only a com1), so "console=com0" is effectively
the same as console=xencons as the latter is what's attached anyway.
GENERIC does see both com0 and com1 though, so the hardware is there:

	com0 at isa0 port 0x3f8-0x3ff irq 4: ns16550a, working fifo
	com1 at isa0 port 0x2f8-0x2ff irq 3: ns16550a, working fifo

I'm guessing that with "/xen console=com1,vga" that the hypervisor hides
the com0 from the dom0.


My latest working /boot.cfg line:

menu=Boot Xen (testing console):load /netbsd-XEN3_DOM0 -v bootdev=dk0 console=xencons;multiboot /xen bootscrub=false dom0=pv,verbose=1 dom0_mem=4G console=com1,vga vga=current console_timestamps=datems dom0_max_vcpus=4 dom0_vcpus_pin=true guest_loglvl=info pv-l1tf=off,domu=off cpuid=rdrand vpmu=on,ipc spec-ctrl=no

The "vga=current" keeps it from clearing the screen so at least the last
messages from /boot remain to comfort one until the network comes up.


Back with Xen-4.13 "/netbsd console=pc" and "/xen console=vga" worked
fine and output from both kernels whizzed by on the iDRAC window.

I read somewhere that XenServer has problems with some hi-res monitors
and that an appropriate mode must be chosen.  I tried "vga=ask", but
other than seeing if a 50-line or other mode would change anything (and
it didn't), I didn't go much further.

BTW, there's a pile of BS, aka "fake news" written about xencons(4) in
the Xen HowTo on the wiki.  I'll write separately about that, again.

--
					Greg A. Woods <gwoods%acm.org@localhost>

Kelowna, BC     +1 250 762-7675           RoboHack <woods%robohack.ca@localhost>
Planix, Inc. <woods%planix.com@localhost>     Avoncote Farms <woods%avoncote.ca@localhost>

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