Re: Xen on RP4

[Elliott Mitchell <ehem+xen@m5p.com>]

On Tue, Nov 24, 2020 at 08:45:32PM -0800, Roman Shaposhnik wrote:
> On Tue, Nov 24, 2020 at 8:41 PM Elliott Mitchell <ehem+xen@m5p.com> wrote:
> >
> > On Tue, Nov 24, 2020 at 08:01:32PM -0800, Roman Shaposhnik wrote:
> > > On Tue, Nov 24, 2020 at 7:37 PM Elliott Mitchell <ehem+xen@m5p.com> wrote:
> > > > Presently I'm using a 5.8 kernel with your patches and haven't seen
> > > > graphical output under Xen with either boot stack.  I've confirmed fully
> > > > operational graphics without Xen on Tianocore, I've confirmed operational
> > > > virtual terminals with U-Boot and not Xen.
> > > >
> > > > I had been planning to wait a bit before moving to 5.9, but if that is
> > > > the crucial ingredient I'll move early.
> > >
> > > We're still using 5.4 -- but it seems that the next LTS 5.10 is also functional.
> > >
> > > I can bet $10 whatever it is -- it is DT related ;-)
> >
> > Given how many of the pieces I'm assembling are alpha or beta level, I
> > estimate a 50:50 chance on that.  Good odds it is device-tree, but good
> > odds I grabbed a bad version of $something.
> >
> > I mostly wanted to know whether I was in completely uncharted territory
> > and needed to wait for others to catch up, versus merely working in a
> > situation where support is funky and I'm at an unknown location in
> > charted territory.
> >
> > I'll be keeping the Tianocore setup available since Xen on ARM really
> > /should/ allow ACPI...
> 
> I don't think you're in the uncharted -- so perhaps a bit of debugging left.
> 
> And, of course, alway feel free to compare what we do -- the image is
> docker pull away.

Actually, since device-tree is very much on my list of concerns, what is
your Xen boot process setup like?

Presently as previously mentioned I'm trying for
U-Boot -> GRUB/EFI -> Xen.  According to the information I currently have
the device-trees are often tied pretty closely to the kernel.  I'm also
using GRUB 2.04 since that has proper support for loading Xen on ARM.

The section of grub.cfg for Linux is roughly:
    linux /boot/vmlinuz-5.8.10-2rp4-6.1.7 root=UUID=01234567-dead-beef-d13d-456789abcdef ro
    devicetree /boot/dtb-5.8.10-2rp4-6.1.7
    initrd /boot/initrd.img-5.8.10-2rp4-6.1.7

My testing section for Xen is:
    xen_hypervisor /boot/xen-4.14-arm64.efi
    xen_module /boot/vmlinuz-5.8.10-2rp4-6.1.7 root=UUID=01234567-dead-beef-d13d-456789abcdef ro
    devicetree /boot/dtb-5.8.10-2rp4-6.1.7
    xen_module --nounzip /boot/initrd.img-5.8.10-2rp4-6.1.7

I've frankly got no idea how to ensure the correct device-tree is passed
to Xen.  Is GRUB's `devicetree` command correct when loading Xen?  Is a
device-tree matched to the Linux kernel appropriate for Xen?

(I'm guessing the second is "yes", but the first I don't have a clue)


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