Re: Xen 4.14.1 on RPI4: device tree generation failed

[Elliott Mitchell <ehem+xen@xxxxxxx>]

On Sun, Jan 31, 2021 at 10:06:21PM -0500, Tamas K Lengyel wrote:
> With rpi-4.19.y kernel and dtbs
> (cc39f1c9f82f6fe5a437836811d906c709e0661c) Xen boots fine and the
> previous error is not present. I get the boot log on the serial with
> just console=hvc0 from dom0 but the kernel ends up in a panic down the
> line:

> This seems to have been caused by a monitor being attached to the HDMI
> port, with HDMI unplugged dom0 boots OK.

The balance of reports seem to suggest 5.10 is the way to go if you want
graphics on a RP4 with Xen.  Even without Xen 4.19 is looking rickety on
RP4.


On Sun, Jan 31, 2021 at 09:43:13PM -0500, Tamas K Lengyel wrote:
> On Sun, Jan 31, 2021 at 8:59 PM Elliott Mitchell <ehem+xen@xxxxxxx> wrote:
> >
> > On Sun, Jan 31, 2021 at 06:50:36PM -0500, Tamas K Lengyel wrote:
> > > On Sun, Jan 31, 2021 at 6:33 PM Elliott Mitchell <ehem+undef@xxxxxxx> 
> > > wrote:
> > > > Presently the rpixen script is grabbing the RPF's 4.19 branch, dates
> > > > point to that last being touched last year.  Their tree is at
> > > > cc39f1c9f82f6fe5a437836811d906c709e0661c.
> > >
> > > I've moved the Linux branch up to 5.10 because there had been a fair
> > > amount of work that went into fixing Xen on RPI4, which got merged
> > > into 5.9 and I would like to be able to build upstream everything
> > > without the custom patches coming with the rpixen script repo.
> >
> > Please keep track of where your kernel source is checked out at since
> > there was a desire to figure out what was going on with the device-trees.
> >
> >
> > Including "console=hvc0 console=AMA0 console=ttyS0 console=tty0" in the
> > kernel command-line should ensure you get output from the kernel if it
> > manages to start (yes, Linux does support having multiple consoles at the
> > same time).
> 
> No output from dom0 received even with the added console options
> (+earlyprintk=xen). The kernel build was from rpi-5.10.y
> c9226080e513181ffb3909a905e9c23b8a6e8f62. I'll check if it still boots
> with 4.19 next.

So, their current HEAD.  This reads like you've got a problematic kernel
configuration.  What procedure are you following to generate the
configuration you use?

Using their upstream as a base and then adding the configuration options
for Xen has worked fairly well for me (`make bcm2711_defconfig`,
`make menuconfig`, `make zImage`).

Notably the options:
CONFIG_PARAVIRT
CONFIG_XEN_DOM0
CONFIG_XEN
CONFIG_XEN_BLKDEV_BACKEND
CONFIG_XEN_NETDEV_BACKEND
CONFIG_HVC_XEN
CONFIG_HVC_XEN_FRONTEND

Should be set to "y".


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