Re: EFI and Xen

[Chuck Zmudzinski <frchuckz%gmail.com@localhost>]

On 5/14/2025 1:33 PM, Manuel Bouyer wrote:
> On Wed, May 14, 2025 at 09:54:35AM -0400, Chuck Zmudzinski wrote:
>> Another odd thing I saw with this system (Intel Raptor Lake i5-14500). I first installed NetBSD 10.1 as a Xen HVM DomU on Xen 4.19.2 distributed by Fedora Linux, with a Fedora 41 Linux PV Dom0 before trying to boot NetBSD PV Dom0 on the pkgsrc version of Xen 4.18. In that configuration, the NetBSD GENERIC kernel did not detect hypervisor0 at mainbus0, and instead detected hyperv0 at cpu0, which would only be valid if the hypervisor was Microsoft Hyper-V instead of Xen! It still boots, but it uses the emulated Qemu devices for disk and network I/O instead of the Xen PV devices. Perhaps this is happening because, according to the information on the NetBSD port-xen HOWTO wiki page, some versions of Xen distributed by Linux distros don't compile Xen with CONFIG_PV_LINEAR_PT, which is required for NetBSD PV support. But I have not checked if Xen 4.19.2 shipped by Fedora is compiled without CONFIG_PV_LINEAR_PT. If Fedora's Xen 4.19.2 does have CONFIG_PV_LINEAR_PT, though, then something strange is happening on my system with Xen because I presume NetBSD/Xen HVM should detect hypervisor0, not hyperv0, when running on Xen with the CONFIG_PV_LINEAR_PT option.
> 
> It's not related to CONFIG_PV_LINEAR_PT, it's probably because Viridian
> is enabled by defaut. You should be able to disable it on a per-guest basis.
> 

Ah, yes I think Viridian is a Microsoft thing and I usually have it on for Windows and Linux HVM guests. I will try turning Viridian off for the NetBSD HVM next time I try it.