Re: [Xen-devel] REGRESSION: Xen 4.13 RC5 fails to bootstrap Dom0 on ARM

From: Stefano Stabellini <sstabellini@kernel.org>
To: Roman Shaposhnik <roman@zededa.com>
Cc: xen-devel@lists.xenproject.org,
	Stefano Stabellini <sstabellini@kernel.org>,
	Stefano Stabellini <stefano.stabellini@xilinx.com>
Subject: Re: [Xen-devel] REGRESSION: Xen 4.13 RC5 fails to bootstrap Dom0 on ARM
Date: Mon, 16 Dec 2019 18:55:10 -0800 (PST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1912161814220.13474@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <CAMmSBy8Zh00tebTvz=__GDv478++b-2t4248YnkH0W9DVgqKbw@mail.gmail.com>

On Mon, 16 Dec 2019, Roman Shaposhnik wrote:
> Hi!
> 
> it appears that something has broken in 4.13 RC5 so that
> I'm now getting the following on ARM (full logs are attached).
> 
> (XEN) ****************************************
> (XEN) Panic on CPU 0:
> (XEN) Failed to allocate requested dom0 memory. 672MB unallocated
> (XEN) ****************************************
> 
> My GRUB boot sequence hasn't changed:
> 
> xen_hypervisor /boot/xen.efi console=dtuart   dom0_mem=1024M,max:1024M
> dom0_max_vcpus=1 dom0_vcpus_pin

FYI we don't actually support the ",max:1024M" part of the dom0_mem
argument on ARM. On ARM, it should just be:

  dom0_mem=1024M

> xen_module /boot/kernel console=hvc0 root=(hd1,gpt1)/rootfs.img text
> devicetree (hd1,gpt4)/eve.dtb
> xen_module (hd1,gpt1)/initrd.img
> 
> In fact, if I use Xen 4.12 instead of 4.13 -- everything seems to work
> as it used to.

I spoke too early: I am unable to reproduce it on my end. On what
platforms did you see this error? Was it the HiKey? Could you please
post the devicetree that you are using (eve.dtb from this example)?

If the dts is this one: https://github.com/lf-edge/eve/blob/master/conf/eve.dts
then I might have an idea. In Xen 4.13 we introduced support for
reserved-memory. It looks like the HiKey has a few reserved-memory
regions and I wonder if that is the problem. Could you please remove the
whole "reserved-memory" node and try again to see if that is the issue?

Also looking at eve.dts above, I am a bit puzzled because the memory
node is:

    memory@0 {
		device_type = "memory";
		reg = <0x0 0x0 0x0 0x5e00000 0x0 0x5f00000 0x0 0x1000 0x0 0x5f02000 0x0 0xefd000 0x0 0x6e00000 0x0 0x60f000 0x0 0x7410000 0x0 0x1aaf0000 0x0 0x22000000 0x0 0x1c000000>;
	};

If I sum all the memory sizes together I get 0x3ddfd000 which is 990M.
If so, I wonder how you could boot succesfully with dom0_mem=1024M even
on Xen 4.12... :-?

If we look at ramoops@21f00000 under reserved-memory:

		ramoops@21f00000 {
			record-size = <0x20000>;
			compatible = "ramoops";
			console-size = <0x20000>;
			reg = <0x0 0x21f00000 0x0 0x100000>;
			ftrace-size = <0x20000>;
		};

the memory range "0x0 0x21f00000 0x0 0x100000" is supposed to fall in
any of the memory ranges of the memory node (the ones I copy/pasted
above). But actually it doesn't. That is a device tree error.

Maybe you could try booting on the HiKey changing the device tree so that the
memory node includes the ramoops range, like this: 

    memory@0 {
		device_type = "memory";
		reg = <0x0 0x0 0x0 0x5e00000 0x0 0x5f00000 0x0 0x1000 0x0 0x5f02000 0x0 0xefd000 0x0 0x6e00000 0x0 0x60f000 0x0 0x7410000 0x0 0x1aaf0000 0x0 0x21f00000 0x0 0x100000 0x0 0x22000000 0x0 0x1c000000>;
	};

(Note that I added "0x0 0x21f00000 0x0 0x100000" to the list of ranges in order.)

Let me know!

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