Re: [Xen-devel] [PATCH 0/1] Dom0less guest device tree format

[Viktor Mitin <viktor.mitin.19@xxxxxxxxx>]

Hi All,

Please be aware that I can confirm the issue.
Current dom0less domU code needs to be fixed.
The issue has been reproduced with several kernel images 4.14.75.
Linux kernel 4.15 image works well without this fix.
Kernel images 4.14.75 and 4.15 works fine with this fix.

Thanks

On Sun, Jul 7, 2019 at 12:12 AM Will Abele <will.abele@xxxxxxxxxx> wrote:
>
> The 07/06/2019 18:19, Julien Grall wrote:
> >
> >
> > On 06/07/2019 19:17, Julien Grall wrote:
> > >
> > >
> > > On 06/07/2019 19:02, Will Abele wrote:
> > >> From: Will Abele <will.abele@xxxxxxxxxx>
> > >>
> > >> Hi,
> > >
> > > Hi,
> > >
> > >> I've been using dom0less Xen on the Hikey 960 with a 4.14 Linux
> > >> Kernel. I had
> > >> trouble getting the 4.14 Linux Kernel to boot as a dom0less domU
> > >> because it was
> > >> misinterpreting the device tree version. Linux 4.14 and earlier
> > >> interpret device
> > >> trees with a "/" in the root node as version 16. Xen produces a
> > >> version 17
> > >> device tree, so the root node needs to be "" to work with 4.14 and
> > >> earlier Linux
> > >> Kernels. Linux 4.15 and later assume that the version is 17, so this
> > >> patch does
> > >> not have any impact.
> > >>
> > >> Please let me know if you need any more information or have
> > >> suggestions for
> > >> other ways to handle this.
> > >
> > > I don't understand where the version comes from. I also don't understand
> > > how you inferred that Xen is creating a version 17 device-tree.
> > >
> > > Do you have link to the paragraph in the specifications?
> >
> > Also, please expand what is the exact error. So we can understand
> > whether this is the right fix.
> >
> > Cheers,
> >
> > --
> > Julien Grall
>
> --
>
> Hi Julien,
>
> Thanks for the prompt response.
>
> I said in my message that Linux was interpreting the device tree as version 
> 16.
> Looking through the code again, I realize it was being interpreted as earlier
> than 16. As mentioned in Linux commit 
> a7e4cfb0a7ca4773e7d0dd1d9c018ab27a15360e,
> Linux had already broken support for FDT versions earlier than 16.
> populate_node() in drivers/of/fdt.c would stop parsing the fdt at the root 
> node
> if it thought the fdt version was earlier than 16.
>
> Xen sets the FDT version to 17 in fdt_create().
>
> The issue I was having was that Linux panicked while initializing interrupts
> because it could not find an interrupt controller. It couldn't find the
> interrupt controller because it didn't process that part of the device tree.
>
> Thanks,
> Will
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