We've been trying to investigate this problem for a while now. We have a Debian box on which at any point in time we run 5/6 VMs. Sometimes one the VMs just randomly go down and we detect this from a ping alert.
This happened this morning and I'm adding in here the xm dmesg output from dom0 (which was NOT what went down) and xm info. Has anyone seen this kind of behavior? Any other info I can provide that helps? And if that needs me to use some tools / commands, pls do let me know.
megha@beta:~$ sudo xm dmesg
(XEN) Xen version 4.0.1 (Debian 4.0.1-1) (
waldi@xxxxxxxxxx) (gcc version 4.4.5 20100824 (prerelease) (Debian 4.4.4-11) ) Fri Sep  3 15:38:12 UTC 2010
 
(XEN) Bootloader: GRUB 1.98+20100804-4
(XEN) Command line: placeholder
(XEN) Video information:
(XEN)  VGA is text mode 80x25, font 8x16
(XEN)  VBE/DDC methods: none; EDID transfer time: 2 seconds
(XEN)  EDID info not retrieved because no DDC retrieval method detected
(XEN) Disc information:
(XEN)  Found 2 MBR signatures
(XEN)  Found 2 EDD information structures
(XEN) Xen-e820 RAM map:
(XEN)  0000000000000000 - 000000000009d000 (usable)
(XEN)  000000000009d000 - 00000000000a0000 (reserved)
(XEN)  00000000000e4000 - 0000000000100000 (reserved)
(XEN)  0000000000100000 - 00000000cff50000 (usable)
(XEN)  00000000cff50000 - 00000000cff65000 (ACPI data)
(XEN)  00000000cff65000 - 00000000cff80000 (ACPI NVS)
(XEN)  00000000cff80000 - 00000000d0000000 (reserved)
(XEN)  00000000e0000000 - 00000000f0000000 (reserved)
(XEN)  00000000fec00000 - 00000000fec10000 (reserved)
(XEN)  00000000fee00000 - 00000000fee01000 (reserved)
(XEN)  00000000ff000000 - 0000000100000000 (reserved)
(XEN)  0000000100000000 - 0000000130000000 (usable)
(XEN) ACPI: RSDP 000F61D0, 0014 (r0 PTLTD )
(XEN) ACPI: RSDT CFF5E9DB, 0078 (r1 PTLTD    RSDT    6040000  LTP        0)
(XEN) ACPI: FACP CFF6440A, 0074 (r1 INTEL  TUMWATER  6040000 PTL         3)
(XEN) ACPI: DSDT CFF60525, 3EE5 (r1  Intel BLAKFORD  6040000 MSFT  3000001)
(XEN) ACPI: FACS CFF65FC0, 0040
(XEN) ACPI: APIC CFF6447E, 0090 (r1 PTLTD  	 APIC    6040000  LTP        0)
(XEN) ACPI: SSDT CFF6450E, 00AF (r5 PTLTD  PTL-MI0   6040000 PTEC        1)
(XEN) ACPI: SPMI CFF645BD, 0041 (r5 PTLTD  PTL-SPMI  6040000 PTL         1)
(XEN) ACPI: MCFG CFF645FE, 003C (r1 PTLTD    MCFG    6040000  LTP        0)
(XEN) ACPI: BOOT CFF6463A, 0028 (r1 PTLTD  $SBFTBL$  6040000  LTP        1)
(XEN) ACPI: SPCR CFF64662, 0050 (r1 PTLTD  $UCRTBL$  6040000 PTL         1)
(XEN) ACPI: SLIC CFF646B2, 0176 (r1 OEMID_ OEMTABLE  6040000  LTP        0)
(XEN) ACPI: ERST CFF64828, 0590 (r1 SMCI   ERSTTBL   6040000 SMCI        1)
(XEN) ACPI: HEST CFF64DB8, 00A8 (r1 SMCI   HESTTBL   6040000 SMCI        1)
(XEN) ACPI: BERT CFF64E60, 0030 (r1 SMCI   BERTTBL   6040000 SMCI        1)
(XEN) ACPI: EINJ CFF64E90, 0170 (r1 SMCI   EINJTBL   6040000 SMCI        1)
(XEN) ACPI: SSDT CFF602C6, 025F (r1  PmRef  Cpu0Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF60220, 00A6 (r1  PmRef  Cpu7Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF6017A, 00A6 (r1  PmRef  Cpu6Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF600D4, 00A6 (r1  PmRef  Cpu5Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF6002E, 00A6 (r1  PmRef  Cpu4Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF5FF88, 00A6 (r1  PmRef  Cpu3Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF5FEE2, 00A6 (r1  PmRef  Cpu2Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF5FE3C, 00A6 (r1  PmRef  Cpu1Tst     3000 INTL 20050228)
(XEN) ACPI: SSDT CFF5EA53, 13E9 (r1  PmRef    CpuPm     3000 INTL 20050228)
(XEN) System RAM: 4094MB (4193204kB)
(XEN) Domain heap initialised
(XEN) Processor #0 7:7 APIC version 20
(XEN) Processor #1 7:7 APIC version 20
(XEN) Processor #2 7:7 APIC version 20
(XEN) Processor #3 7:7 APIC version 20
(XEN) IOAPIC[0]: apic_id 4, version 32, address 0xfec00000, GSI 0-23
(XEN) IOAPIC[1]: apic_id 5, version 32, address 0xfec80000, GSI 24-47
(XEN) Enabling APIC mode:  Flat.  Using 2 I/O APICs
(XEN) Using scheduler: SMP Credit Scheduler (credit)
(XEN) Detected 2666.801 MHz processor.
(XEN) Initing memory sharing.
(XEN) VMX: Supported advanced features:
(XEN)  - APIC MMIO access virtualisation
(XEN)  - APIC TPR shadow
(XEN)  - Virtual NMI
(XEN)  - MSR direct-access bitmap
(XEN) HVM: ASIDs disabled.
(XEN) HVM: VMX enabled
(XEN) I/O virtualisation disabled
(XEN) Total of 4 processors activated.
(XEN) ENABLING IO-APIC IRQs
(XEN)  -> Using new ACK method
(XEN) checking TSC synchronization across 4 CPUs: passed.
(XEN) Platform timer appears to have unexpectedly wrapped 1 times.
(XEN) Platform timer is 3.579MHz ACPI PM Timer
(XEN) Allocated console ring of 16 KiB.
(XEN) Brought up 4 CPUs
(XEN) CPUIDLE: disabled due to no HPET. Force enable with 'cpuidle'.
(XEN) *** LOADING DOMAIN 0 ***
(XEN)  Xen  kernel: 64-bit, lsb, compat32
(XEN)  Dom0 kernel: 64-bit, PAE, lsb, paddr 0x1000000 -> 0x16b1000
(XEN) PHYSICAL MEMORY ARRANGEMENT:
(XEN)  Dom0 alloc.:   0000000128000000->000000012c000000 (985849 pages to be allocated)
(XEN) VIRTUAL MEMORY ARRANGEMENT:
(XEN)  Loaded kernel: ffffffff81000000->ffffffff816b1000
(XEN)  Init. ramdisk: ffffffff816b1000->ffffffff832b4600
(XEN)  Phys-Mach map: ffffffff832b5000->ffffffff83a5a7c8
(XEN)  Start info:    ffffffff83a5b000->ffffffff83a5b4b4
(XEN)  Page tables:   ffffffff83a5c000->ffffffff83a7d000
(XEN)  Boot stack:    ffffffff83a7d000->ffffffff83a7e000
(XEN)  TOTAL:         ffffffff80000000->ffffffff83c00000
(XEN)  ENTRY ADDRESS: ffffffff81502200
(XEN) Dom0 has maximum 4 VCPUs
(XEN) Scrubbing Free RAM: .done.
(XEN) Xen trace buffers: disabled
(XEN) Std. Loglevel: Errors and warnings
(XEN) Guest Loglevel: Nothing (Rate-limited: Errors and warnings)
(XEN) Xen is relinquishing VGA console.
(XEN) *** Serial input -> DOM0 (type 'CTRL-a' three times to switch input to Xen)
(XEN) Freed 176kB init memory.