Re: port-amd64/55543: PVHVM fails to attach hypervisor bus on Amazon EC2 t2.micro

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

On Sun, Sep 06, 2020 at 02:50:32PM -0300, Jared McNeill wrote:
> On Sun, 6 Sep 2020, Manuel Bouyer wrote:
> 
> > On Sun, Sep 06, 2020 at 02:31:23PM +0200, Manuel Bouyer wrote:
> > > Unfortunably with Xen 4.2.5 it boots. Also, xencons is present.
> > > 
> > > Can you enter ddb when it's hung ? if so, can you see where the Xen-related
> > > threads are waiting ?
> > 
> > Also, enabling the DPRINTK macro in xenbus/xenbus_probe.c could give
> > hints.
> 
> I don't see any output from DPRINTK so I guess we are hung before the thread
> had an opportunity to run. Unfortunately console input is not supported on
> EC2 so I can't get to ddb.

OK, so we have to make guesses.
acpicpu0 is attached via config_defer() so I guess it doens't need
threads to be running. On my test systems, after acpicpu0 there are
xen devices and uhub0.
Maybe the clock isn't fully functionnal ? Can you try commenting out
the delay_func/x86_initclock_func override in xen_hvm_init() (carefull,
there is also this code in init_xen_early(), this one isn't used
for HVM).

--- xen/hypervisor.c.orig	2020-09-07 12:48:12.005563460 +0200
+++ xen/hypervisor.c	2020-09-07 12:46:25.405240796 +0200
@@ -438,8 +438,10 @@
 		xen_start_info.console.domU.evtchn = xen_hvm_param.value;
 	}
 
+#if 0
 	delay_func = x86_delay = xen_delay;
 	x86_initclock_func = xen_initclocks;
+#endif
 
 	vm_guest = VM_GUEST_XENPVHVM; /* Be more specific */
 	return 1;

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