Re: [Xen-devel] Cannot start up HVM guest when maxmem is not equal to memory and HAP is enabled.

[Yufang Zhang <yufang521247@xxxxxxxxx>]

2012/1/11 George Dunlap <George.Dunlap@xxxxxxxxxxxxx>

On Wed, Jan 11, 2012 at 8:03 AM, Yufang Zhang <yufang521247@xxxxxxxxx> wrote:
> Hi all,
>
> On my production deployment with xen-3.4.4-rc1, HVM guest would not start up
> when maxmem is set not equal to memory, unless HAP is disable(hap=0). The
> guest just hangs at 'Booting from Hard Disk...' as shown in the attachment.

Is there a reason you want to set maxmem != memory?  Starting in 4.0,
this will cause the VM to boot in "populate-on-demand" mode; but I
think in 3.4, this may have undefined behavior.

Actually, you would be exposed to this problem whenever you restart xend and then reboot the hvm guest, even you set  maxmem == memory in the config file of that guest. When xend is restarted, it tries to recreate guest information. memory_dynamic_max and memory_static_max, which are used to calculate memory and maxmem, are re-calculated from mem_kb and maxmem_kb respectively.  mem_kb is not equal to maxmem_kb. Thus memory != maxmem after xend restarts, and rebooting this hvm guest later would leads guest crash/hang.   

> I find that both Oracle VM and Fedora have the same problem per the
> following links:
>
> http://docs.oracle.com/cd/E15458_01/doc.22/e15443/toc.htm#BABBIBFD
> http://docs.oracle.com/cd/E26996_01/e18546/CJAGDAGB.html#id419003
> https://bugzilla.redhat.com/show_bug.cgi?id=645319
>
> Could I ask if there is any work in upstream/xen-unstable to fix this
> problem?

Setting maxmem != memory in 4.1 will definitely have a different
effect -- if your guest has a balloon driver, you will start your VM
"pre-ballooned"; if your guest does not, it will crash as soon as it
dirties more than "memory" amount of memory.

 -George

I check the xend code of xen-unstable,  the related logic didn't change since xen-3.4. So I *guess* a hvm guest without balloon driver would crash after some time(when it dirties enough memory) after you restarting xend and rebooting the guest on xen-4.1.

>
> Thanks.
>
> Below is the xm dmesg output related with the hvm guest:
> (XEN) HVM3: HVM Loader
> (XEN) HVM3: Detected Xen v3.4.4-rc1-pre
> (XEN) HVM3: CPU speed is 2267 MHz
> (XEN) irq.c:243: Dom3 PCI link 0 changed 0 -> 5
> (XEN) HVM3: PCI-ISA link 0 routed to IRQ5
> (XEN) irq.c:243: Dom3 PCI link 1 changed 0 -> 10
> (XEN) HVM3: PCI-ISA link 1 routed to IRQ10
> (XEN) irq.c:243: Dom3 PCI link 2 changed 0 -> 11
> (XEN) HVM3: PCI-ISA link 2 routed to IRQ11
> (XEN) irq.c:243: Dom3 PCI link 3 changed 0 -> 5
> (XEN) HVM3: PCI-ISA link 3 routed to IRQ5
> (XEN) HVM3: pci dev 01:2 INTD->IRQ5
> (XEN) HVM3: pci dev 01:3 INTA->IRQ10
> (XEN) HVM3: pci dev 03:0 INTA->IRQ5
> (XEN) HVM3: pci dev 04:0 INTA->IRQ5
> (XEN) HVM3: pci dev 02:0 bar 10 size 02000000: f0000008
> (XEN) HVM3: pci dev 03:0 bar 14 size 01000000: f2000008
> (XEN) HVM3: pci dev 02:0 bar 14 size 00001000: f3000000
> (XEN) HVM3: pci dev 03:0 bar 10 size 00000100: 0000c001
> (XEN) HVM3: pci dev 04:0 bar 10 size 00000100: 0000c101
> (XEN) HVM3: pci dev 04:0 bar 14 size 00000100: f3001000
> (XEN) HVM3: pci dev 01:2 bar 20 size 00000020: 0000c201
> (XEN) HVM3: pci dev 01:1 bar 20 size 00000010: 0000c221
> (XEN) HVM3: Multiprocessor initialisation:
> (XEN) HVM3:  - CPU0 ... 40-bit phys ... fixed MTRRs ... var MTRRs [2/8] ...
> done.
> (XEN) HVM3: Writing SMBIOS tables ...
> (XEN) HVM3: Loading ROMBIOS ...
> (XEN) HVM3: 10332 bytes of ROMBIOS high-memory extensions:
> (XEN) HVM3:   Relocating to 0xfc000000-0xfc00285c ... done
> (XEN) HVM3: Creating MP tables ...
> (XEN) HVM3: Loading Cirrus VGABIOS ...
> (XEN) HVM3: Loading PCI Option ROM ...
> (XEN) HVM3:  - Manufacturer: http://etherboot.org
> (XEN) HVM3:  - Product name: gPXE
> (XEN) HVM3: Loading ACPI ...
> (XEN) HVM3:  - Lo data: 000ea020-000ea04f
> (XEN) HVM3:  - Hi data: fc002c00-fc0060bf
> (XEN) HVM3: vm86 TSS at fc006400
> (XEN) HVM3: BIOS map:
> (XEN) HVM3:  c0000-c8fff: VGA BIOS
> (XEN) HVM3:  c9000-d57ff: Etherboot ROM
> (XEN) HVM3:  eb000-eb150: SMBIOS tables
> (XEN) HVM3:  f0000-fffff: Main BIOS
> (XEN) HVM3: Invoking ROMBIOS ...
> (XEN) HVM3: $Revision: 1.221 $ $Date: 2008/12/07 17:32:29 $
> (XEN) stdvga.c:147:d3 entering stdvga and caching modes
> (XEN) HVM3: VGABios $Id: vgabios.c,v 1.67 2008/01/27 09:44:12 vruppert Exp $
> (XEN) HVM3: Bochs BIOS - build: 06/23/99
> (XEN) HVM3: $Revision: 1.221 $ $Date: 2008/12/07 17:32:29 $
> (XEN) HVM3: Options: apmbios pcibios eltorito PMM
> (XEN) HVM3:
> (XEN) HVM3: ata0-0: PCHS=16383/16/63 translation=lba LCHS=1024/255/63
> (XEN) HVM3: ata0 master: QEMU HARDDISK ATA-7 Hard-Disk (8192 MBytes)
> (XEN) HVM3: IDE time out
> (XEN) HVM3:
> (XEN) HVM3:
> (XEN) HVM3:
> (XEN) HVM3: Press F12 for boot menu.
> (XEN) HVM3:
> (XEN) HVM3: Booting from Hard Disk...
> (XEN) HVM3: Booting from 0000:7c00
> (XEN) io.c:199:d3 MMIO emulation failed @ 0008:4013b1: 90 86 95 21 08 83
>

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