Re: NetBSD 10.0 RC1 PVH and XenServer/XCP

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

On Tue, Nov 14, 2023 at 09:55:55AM +0000, Stephen Borrill wrote:
> On Tue, 14 Nov 2023, Stephen Borrill wrote:
> > On Mon, 13 Nov 2023, Brian Buhrow wrote:
> > > 	hello.  If you place an uncompressed copy of netbsd-INSTALL.gz from
> > > the kernels directory of a
> > > release build as /netbsd on the iso image that you boot from, do you
> > > then find you can boot
> > > and, then, format and populate the xbd disk that shows up?  I've
> > > done this to build NetBSD
> > > systems under hosted VM offerings, specifically Linode's offerings.
> > 
> > I expect this would get the installer going, but without the cd being
> > accessible, I would have to resort to trying to fetch the sets over the
> > network. Lack of access to the ISO library may cause problems later too.
> > 
> > In PVH mode, the cdrom device is present in the xenstore at all times,
> > but its status does not change when an ISO image is inserted:
> > 
> > # xenstore-read domid
> > 11
> > # xenstore-ls /local/domain/20/device/vbd
> > [snip]
> > 5696 = ""
> > backend = "/local/domain/0/backend/vbd3/20/5696"
> > backend-id = "0"
> > device-type = "cdrom"
> > state = "1"
> > virtual-device = "5696"
> > 
> > Compare this to PV mode. The vbd only appears when the ISO image is
> > inserted, but looks like this:
> > 
> > # xenstore-read domid
> > 11
> > # xenstore-ls /local/domain/11/device/vbd
> > [snip]
> > 51760 = ""
> > backend = "/local/domain/0/backend/vbd3/11/51760"
> > backend-id = "0"
> > device-type = "cdrom"
> > event-channel = "19"
> > protocol = "x86_64-abi"
> > ring-ref = "494"
> > state = "4"
> > virtual-device = "51760"
> > 
> > From this it is clear the PVH device is not properly initialised and a
> > clue to this is found in dmesg:
> > xenbus0: ignoring device/vbd/5696 type cdrom
> 
> Comparing to a Linux PVH VM, I can see my logic isn't quite right. The
> device, as listed in the xenstore, is identical to that found on NetBSD.
> Nothing changes in the xenstore as a result of inserting an ISO.
> 
> The device is explicitly skipped:
> https://nxr.netbsd.org/xref/src/sys/arch/xen/xenbus/xenbus_probe.c#455
> 
> Is this because xbd doesn't have the concept of 'not ready'?

Mainly because (as the commit log says) the emulated device isn't
disabled so the virtual cd would show up as both cd0 and an xbd instance.

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