[Xen-devel] Xen on ARM: "Failed to allocate contiguous memory for dom0" with dom0_mem greater than 256MB

[Arianna Avanzini <avanzini.arianna@xxxxxxxxx>]

Hello,

my name's Arianna and, for my master thesis at University of Modena (with Paolo
Valente, in Italy, [1]), I'm porting an automotive grade real-time OS
(Evidence's Erika [2], [3]) on Xen on ARM. I'm running Xen on a cubieboard2,
featuring an Allwinner A20 chip and 1GB of RAM.

I compiled from source both Xen (from staging, my current head is commit
231d7f4) and Linux (from linux-sunxi/sunxi-devel merged with torvalds/master, my
head is commit df32e43), as a dom0 kernel. I was also able to start a PV domU
with the same kernel, which I built with both dom0 and domU options enabled.

I noticed that Xen 4.4 fails to boot the dom0 if more than 256MB of RAM are
assigned to it by providing the dom0_mem boot option. The error message produced
during the boot process is the following.

Xen heap: 0000000076000000-000000007e000000 (32768 pages)
Dom heap: 229376 pages
Looking for UART console serial0
 Xen 4.4-rc2
(XEN) Xen version 4.4-rc2 (ava@) (armv7a-hardfloat-linux-gnueabi-gcc (Gentoo
4.7.3 p1.0, pie-0.5.5) 4.7.3) debug=y Fri Jan 24 10:46:18 CET 2014
(XEN) Latest ChangeSet: Thu Jan 23 10:30:08 2014 +0100 git:231d7f4
(XEN) Console output is synchronous.
(XEN) Processor: 410fc074: "ARM Limited", variant: 0x0, part 0xc07, rev 0x4
(XEN) 32-bit Execution:
(XEN)   Processor Features: 00001131:00011011
(XEN)     Instruction Sets: AArch32 Thumb Thumb-2 ThumbEE Jazelle
(XEN)     Extensions: GenericTimer Security
(XEN)   Debug Features: 02010555
(XEN)   Auxiliary Features: 00000000
(XEN)   Memory Model Features: 10101105 40000000 01240000 02102211
(XEN)  ISA Features: 02101110 13112111 21232041 11112131 10011142 00000000
(XEN) Platform: Allwinner A20
(XEN) Generic Timer IRQ: phys=30 hyp=26 virt=27
(XEN) Using generic timer at 24000 KHz
(XEN) GIC initialization:
(XEN)         gic_dist_addr=0000000001c81000
(XEN)         gic_cpu_addr=0000000001c82000
(XEN)         gic_hyp_addr=0000000001c84000
(XEN)         gic_vcpu_addr=0000000001c86000
(XEN)         gic_maintenance_irq=25
(XEN) GIC: 160 lines, 2 cpus, secure (IID 0100143b).
(XEN) Using scheduler: SMP Credit Scheduler (credit)
(XEN) Allocated console ring of 16 KiB.
(XEN) VFP implementer 0x41 architecture 2 part 0x30 variant 0x7 rev 0x4
(XEN) Bringing up CPU1
(XEN) Failed to bring up CPU1
(XEN) Failed to bring up CPU 1 (error -19)
(XEN) Brought up 1 CPUs
(XEN) *** LOADING DOMAIN 0 ***
(XEN)
(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) Failed to allocate contiguous memory for dom0
(XEN) ****************************************
(XEN)
(XEN) Reboot in five seconds...

After a short search on the xen-devel mailing list, I found a discussion which I
believe might be related to this issue:
http://lists.xen.org/archives/html/xen-devel/2013-12/msg02239.html.
However, from that thread, I wasn't able to extrapolate a solution to the said
issue (not even to understand whether it is a bug or a feature, actually). You
can find attached to this mail the complete logs of a successful boot (with
dom0_mem=256M) and a failing boot (with dom0_mem=512M). If interesting, I'd be
glad to help investigate that, e.g., by providing further logs or by testing
patches.

Thank you,
Arianna



[1] http://www.unimore.it/
[2] http://www.evidence.eu.com/
[3] http://erika.tuxfamily.org/drupal/


-- 
/*
 * Arianna Avanzini
 * avanzini.arianna@xxxxxxxxx
 * 73628@xxxxxxxxxxxxxxxxxxx
 */

Attachment: failing-boot-dom0_mem-512.log
Description: Text Data

Attachment: successful-boot-dom0_mem-256.log
Description: Text Data

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