Re: kern/57790: Kernel panic on install

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

Dean: Can you run with serial console rather than graphical console
and record the entire output?  That may help to gather more
information about the environment that NetBSD is booting in.


Relevant fragment of stack trace:

panic
xengnt_finish_init() at netbsd:xengnt_finish_init+0x22f
xengnt_init
hypervisor_attach
config_attach_internal
config_found
xen_mainbus_attach
mainbus_attach
config_attach_internal
config_rootfound
cpu_configure
main

There's only one panic in xengnt_finish_init:

	while (gnt_nr_grant_frames < previous_nr_grant_frames) {
		if (xengnt_more_entries() != 0)
			panic("xengnt_resume: can't restore grant frames");
	}

So although it's not printed on screen, I think that must be what
crashed.

There are three ways xengnt_more_entries can fail:

1. gnt_nr_grant_frames == gnt_max_grant_frames
2. kmem_alloc(KM_NOSLEEP) fails
3. HYPERVISOR_grant_table_op(GNTTABOP_setup_table, ...) returns a
   status other than GNTST_okay

(In all three cases, it returns ENOMEM, so printing the error code in
the panic message wouldn't help even if we could see the panic
message.)

Can we get someone who knows the Xen grant table logic to look at
this and figure out what's happening here?

If it's case (2), it may just be that the VM doesn't have enough RAM
reserved to boot NetBSD.  Not sure we should be using KM_NOSLEEP in
this path.