I've compiled unstable c/s: 5d20d2f6ffed and linux 3.2.9 but I've been 
experiencing a couple of panics since. Two times I was able to 
reproduce the crash by simply running upgrade-grub2 after fiddling 
with linux/xen cmdline options, but I noticed it does also crash on 
other (less known) occasions. No VMs have been setup yet, so it's 
purely a domain 0 setup so far.

Attaching the relevant files, in the hope they may help understanding 
the cause of this. 

- xl-dmesg.out
- dmidecode.out
- lspci-vvv.out
- 3.2.9-config

Goncalo

[  197.398425] BUG: unable to handle kernel paging request at 000012b7
[  197.398794] IP: [<c1269dae>] is_xen_swiotlb_buffer+0x35/0x80
[  197.399085] *pdpt = 0000000000000000 *pde = 0000000000000000 
[  197.399406] Oops: 0000 [#1] SMP 
[  197.399720] Modules linked in: dm_mod binfmt_misc loop processor 
thermal_sys hwmon button sd_mod mptsas mptscsih mptbase 
scsi_transport_sas bnx2 scsi_mod [last unloaded: scsi_wait_scan]
[  197.400971] 
[  197.401213] Pid: 0, comm: swapper/0 Tainted: G        W    3.2.9 #9 
Dell Inc. PowerEdge R310/05XKKK
[  197.401779] EIP: 0061:[<c1269dae>] EFLAGS: 00010206 CPU: 0
[  197.402030] EIP is at is_xen_swiotlb_buffer+0x35/0x80
[  197.402280] EAX: 00000063 EBX: ffffffff ECX: c1779000 EDX: ffffffff
[  197.402534] ESI: 00000000 EDI: 00000002 EBP: 00000000 ESP: e3c0fec4
[  197.402805]  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
[  197.403055] Process swapper/0 (pid: 0, ti=e3c0e000 task=c1641060 
task.ti=c163a000)
[  197.403513] Stack:
[  197.403756]  00000000 00000000 c1269e38 ffffffff e3e2a860 00000092 
c5790480 f017e220
[  197.404510]  c1269efb c5b0a0c0 c1269f0a 00000092 00000002 00000000 
eda6757c 00000092
[  197.405245]  00000002 04450000 00000000 00000444 00000000 00000000 
00000000 00000544
[  197.405985] Call Trace:
[  197.406233]  [<c1269e38>] ? xen_swiotlb_sync_single+0x3f/0x7b
[  197.406488]  [<c1269efb>] ? 
xen_swiotlb_sync_single_for_device+0x13/0x13
[  197.406744]  [<c1269f0a>] ? 
xen_swiotlb_sync_single_for_cpu+0xf/0x13
[  197.407026]  [<eda6757c>] ? bnx2_rx_int+0xf5/0x3de [bnx2]
[  197.407286]  [<eda678b3>] ? bnx2_poll_work+0x4e/0x56 [bnx2]
[  197.407537]  [<eda679a3>] ? bnx2_poll+0x5f/0xe7 [bnx2]
[  197.407788]  [<c1047372>] ? irq_enter+0x49/0x49
[  197.408037]  [<c13083f6>] ? net_rx_action+0xb8/0x1d6
[  197.408307]  [<c1047372>] ? irq_enter+0x49/0x49
[  197.408556]  [<c104741a>] ? __do_softirq+0xa8/0x168
[  197.408805]  [<c1047372>] ? irq_enter+0x49/0x49
[  197.409052]  <IRQ> 
[  197.409332]  [<c1047248>] ? irq_exit+0x2f/0x91
[  197.409588]  [<c126234e>] ? xen_evtchn_do_upcall+0x1d/0x26
[  197.409843]  [<c13d18c7>] ? xen_do_upcall+0x7/0xc
[  197.410095]  [<c106007b>] ? update_wall_time+0xa0/0x3ef
[  197.410348]  [<c10023a7>] ? hypercall_page+0x3a7/0x1000
[  197.410601]  [<c1006772>] ? xen_safe_halt+0xf/0x1b
[  197.410852]  [<c10137b4>] ? default_idle+0x65/0xb8
[  197.411122]  [<c100c2c3>] ? cpu_idle+0x61/0x7e
[  197.411373]  [<c16787f5>] ? start_kernel+0x34a/0x34d
[  197.411627]  [<c167a258>] ? xen_start_kernel+0x554/0x55b
[  197.411875] Code: ff ff ff 89 c3 e8 09 d6 d9 ff 39 f0 b8 ff ff ff 
ff 0f 45 d8 89 d8 c1 e8 0e 0f be 80 e0 44 67 c1 85 c0 78 4d 8b 14 85 
c0 44 67 c1 <8b> 82 b8 12 00 00 03 82 b0 12 00 00 39 c3 73 36 a1 28  
[  197.414841] EIP: [<c1269dae>] is_xen_swiotlb_buffer+0x35/0x80 
SS:ESP 0069:e3c0fec4
[  197.420448] CR2: 00000000000012b7
[  197.420711] ---[ end trace 4eaa2a86a8e2da48 ]---
[  197.420962] Kernel panic - not syncing: Fatal exception in 
interrupt
[  197.421214] Pid: 0, comm: swapper/0 Tainted: G      D W    3.2.9 #9
[  197.421466] Call Trace:
[  197.421709]  [<c13ce57c>] ? panic+0x4d/0x157
[  197.421958]  [<c100efc4>] ? oops_end+0xad/0xb8
[  197.422226]  [<c102a930>] ? bad_area_nosemaphore+0xa/0xc
[  197.422474]  [<c102ad3d>] ? do_page_fault+0x167/0x31a
[  197.422726]  [<c11fe40d>] ? cpumask_next_and+0x20/0x2b
[  197.422975]  [<c1029b90>] ? pvclock_clocksource_read+0xec/0x11e
[  197.423230]  [<c100b840>] ? __spin_time_accum+0x26/0x36
[  197.423502]  [<c100ba6f>] ? __xen_spin_lock+0xb4/0xc8
[  197.423754]  [<c100673c>] ? xen_force_evtchn_callback+0xc/0x10
[  197.424008]  [<c102abd6>] ? vmalloc_sync_all+0xb6/0xb6
[  197.424261]  [<c13d106e>] ? error_code+0x5a/0x60
[  197.424512]  [<c102abd6>] ? vmalloc_sync_all+0xb6/0xb6
[  197.424763]  [<c1269dae>] ? is_xen_swiotlb_buffer+0x35/0x80
[  197.425034]  [<c1269e38>] ? xen_swiotlb_sync_single+0x3f/0x7b
[  197.425289]  [<c1269efb>] ? 
xen_swiotlb_sync_single_for_device+0x13/0x13
[  197.425545]  [<c1269f0a>] ? 
xen_swiotlb_sync_single_for_cpu+0xf/0x13
[  197.425801]  [<eda6757c>] ? bnx2_rx_int+0xf5/0x3de [bnx2]
[  197.426054]  [<eda678b3>] ? bnx2_poll_work+0x4e/0x56 [bnx2]
[  197.426328]  [<eda679a3>] ? bnx2_poll+0x5f/0xe7 [bnx2]
[  197.426579]  [<c1047372>] ? irq_enter+0x49/0x49
[  197.426830]  [<c13083f6>] ? net_rx_action+0xb8/0x1d6
[  197.427083]  [<c1047372>] ? irq_enter+0x49/0x49
[  197.427337]  [<c104741a>] ? __do_softirq+0xa8/0x168
[  197.427590]  [<c1047372>] ? irq_enter+0x49/0x49
[  197.427853]  <IRQ>  [<c1047248>] ? irq_exit+0x2f/0x91
[  197.428149]  [<c126234e>] ? xen_evtchn_do_upcall+0x1d/0x26
[  197.428410]  [<c13d18c7>] ? xen_do_upcall+0x7/0xc
[  197.428668]  [<c106007b>] ? update_wall_time+0xa0/0x3ef
[  197.428920]  [<c10023a7>] ? hypercall_page+0x3a7/0x1000
[  197.429191]  [<c1006772>] ? xen_safe_halt+0xf/0x1b
[  197.429446]  [<c10137b4>] ? default_idle+0x65/0xb8
[  197.429695]  [<c100c2c3>] ? cpu_idle+0x61/0x7e
[  197.429941]  [<c16787f5>] ? start_kernel+0x34a/0x34d
[  197.430189]  [<c167a258>] ? xen_start_kernel+0x554/0x55b
(XEN) Domain 0 crashed: rebooting machine in 5 seconds.