Re: -current doesn't boot on xen

[Jaromír Doleček <jaromir.dolecek%gmail.com@localhost>]

Le sam. 30 janv. 2021 à 20:22, <coypu%sdf.org@localhost> a écrit :
> [     1.000000] hypervisor0 at mainbus0: Xen version 4.14.0.88.g1d1d1f53
> ...
>
> If I ask their interface for more information:
>
> Command result:
>         Virtualization mode: Paravirtualized
>         Memory: 10240 MiB
>         VCPUs: 4
>         Total disk: 120.0 GiB
>         Last installed OS: NetBSD 8.2 - 64 bit
>         Boot option: PV-GRUB - 64 bit
>         Boot arguments: (hd0,0)/boot/grub/menu.lst
>         Live migration: enabled

According to the boot messages, it seems they use Xen 4.14 which is
surely new enough to support gnttab v2.

Can you check with them if they by chance disabled v2 for your host?
There exists a 'gnttab' option for this, which can restrict the
maximum possible version. I don't know why anybody would like to set
it, but the possibility is there.

Fallback to v1 is not really desirable - it's slower as it requires
more synchronization, and also you lose support for sub-page grants,
which are nice as an optimization particularly for networking. The
bigger frame support in v2 is not really relevant - that's only needed
for very big DomUs (like several TB RAM). It's not the reason we use
v2 now.

Jaromir