[Xen-devel] repeating 'd1v0 Over-allocation for domain 1' messages in xen 4.7 Host logs on PVHVM Guest launch

[PGNet Dev <pgnet.dev@xxxxxxxxx>]

(relo'd from user list)

I've launched an Ubuntu PVHVM guest, on a Xen 4.7 host

    cat guest1.cfg
        name                 = 'guest1'
        builder              = 'hvm'
        xen_platform_pci     = 1
        device_model_version = 'qemu-xen'
        bios                 = 'ovmf'
        bios_override        = '/usr/share/qemu/ovmf-x86_64.bin'
        ...

On guest launch, `xl dmesg` in host reports

    ...
    (XEN) [2016-06-27 21:54:09] HVM1 restore: CPU 0
    (d1) [2016-06-27 21:54:10] HVM Loader
    (d1) [2016-06-27 21:54:10] Detected Xen v4.7.0_08-452
    (d1) [2016-06-27 21:54:10] Xenbus rings @0xfeffc000, event channel 1
    (d1) [2016-06-27 21:54:10] System requested OVMF
    (d1) [2016-06-27 21:54:10] CPU speed is 3093 MHz
    (d1) [2016-06-27 21:54:10] Relocating guest memory for lowmem MMIO 
space disabled
    (d1) [2016-06-27 21:54:10] PCI-ISA link 0 routed to IRQ5
    (d1) [2016-06-27 21:54:10] PCI-ISA link 1 routed to IRQ10
    (d1) [2016-06-27 21:54:10] PCI-ISA link 2 routed to IRQ11
    (d1) [2016-06-27 21:54:10] PCI-ISA link 3 routed to IRQ5
    (d1) [2016-06-27 21:54:10] pci dev 01:3 INTA->IRQ10
    (d1) [2016-06-27 21:54:10] pci dev 02:0 INTA->IRQ11
    (d1) [2016-06-27 21:54:10] pci dev 04:0 INTA->IRQ5
    (d1) [2016-06-27 21:54:10] No RAM in high memory; setting high_mem 
resource base to 100000000
    (d1) [2016-06-27 21:54:10] pci dev 02:0 bar 14 size 001000000: 
0f0000008
    (d1) [2016-06-27 21:54:10] pci dev 03:0 bar 10 size 001000000: 
0f1000008
    (d1) [2016-06-27 21:54:10] pci dev 04:0 bar 30 size 000040000: 
0f2000000
    (d1) [2016-06-27 21:54:10] pci dev 04:0 bar 10 size 000020000: 
0f2040000
    (d1) [2016-06-27 21:54:10] pci dev 03:0 bar 30 size 000010000: 
0f2060000
    (d1) [2016-06-27 21:54:10] pci dev 03:0 bar 18 size 000001000: 
0f2070000
    (d1) [2016-06-27 21:54:10] pci dev 02:0 bar 10 size 000000100: 
00000c001
    (d1) [2016-06-27 21:54:10] pci dev 04:0 bar 14 size 000000040: 
00000c101
    (d1) [2016-06-27 21:54:10] pci dev 01:1 bar 20 size 000000010: 
00000c141
    (d1) [2016-06-27 21:54:10] Multiprocessor initialisation:
    (d1) [2016-06-27 21:54:10]  - CPU0 ... 39-bit phys ... fixed MTRRs 
... var MTRRs [1/8] ... done.
    (d1) [2016-06-27 21:54:10] Writing SMBIOS tables ...
    (d1) [2016-06-27 21:54:10] Loading OVMF ...
    (XEN) [2016-06-27 21:54:10] d1v0 Over-allocation for domain 1: 
524545 > 524544
    (d1) [2016-06-27 21:54:10] Loading ACPI ...
    (d1) [2016-06-27 21:54:10] vm86 TSS at fc009f00
    (d1) [2016-06-27 21:54:10] BIOS map:
    (d1) [2016-06-27 21:54:10]  ffe00000-ffffffff: Main BIOS
    (d1) [2016-06-27 21:54:10] E820 table:
    (d1) [2016-06-27 21:54:10]  [00]: 00000000:00000000 - 
00000000:000a0000: RAM
    (d1) [2016-06-27 21:54:10]  HOLE: 00000000:000a0000 - 00000000:000f0000
    (d1) [2016-06-27 21:54:10]  [01]: 00000000:000f0000 - 
00000000:00100000: RESERVED
    (d1) [2016-06-27 21:54:10]  [02]: 00000000:00100000 - 
00000000:7eeb6000: RAM
    (d1) [2016-06-27 21:54:10]  HOLE: 00000000:7eeb6000 - 00000000:fc000000
    (d1) [2016-06-27 21:54:10]  [03]: 00000000:fc000000 - 
00000001:00000000: RESERVED
    (d1) [2016-06-27 21:54:10] Invoking OVMF ...

At this point, the guest's up

    xl list
        Name                                        ID   Mem VCPUs 
State  Time(s)
        Domain-0                                     0  4096     1 
r-----     31.1
        guest1                                       1  2049     1 
-b----     17.4
, accessible and functional.,

    uname -a
        Linux guest1 4.4.0-24-generic #43-Ubuntu SMP Wed Jun 8 19:27:37 
UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

As long as the guest is up, the Host logs continuously fill up with 
over-allocation errors.

    xl dmesg
        (XEN) [2016-06-27 21:54:32] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:54:32] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:54:34] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:54:38] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:54:46] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:55:02] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:55:35] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:56:07] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:56:39] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:57:11] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:57:43] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:58:15] d1v0 Over-allocation for domain 1: 
524545 > 524544
        (XEN) [2016-06-27 21:58:47] d1v0 Over-allocation for domain 1: 
524545 > 524544
        ...

with multiple guests, it quickly gets ridiculous,

     xl dmesg | grep -i Over-allocation | wc -l
        22787

What are these 'Over-allocation' messages?

What needs to be fixed, or if of no concern, can these messages be silenced?

Happy to provide any identified additional logs.

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