Hi,

I was getting this BUG while running into a GPF:

BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-x86/2248
caller is arch_trigger_all_cpu_backtrace_handler+0x1d/0xf7
Pid: 2248, comm: qemu-system-x86 Not tainted 2.6.36+ #12
Call Trace:
[<ffffffff81203194>] debug_smp_processor_id+0xd8/0xf4
[<ffffffff813803ab>] arch_trigger_all_cpu_backtrace_handler+0x1d/0xf7
[<ffffffff81381e64>] notifier_call_chain+0xa4/0xdb
[<ffffffff81381efe>] __atomic_notifier_call_chain+0x63/0x95
[<ffffffff81381e9b>] ? __atomic_notifier_call_chain+0x0/0x95
[<ffffffff81381cfb>] ? sub_preempt_count+0x97/0xaa
[<ffffffff8121de8c>] ? pfn_to_dma_pte+0x73/0x190
[<ffffffff81381f44>] atomic_notifier_call_chain+0x14/0x16
[<ffffffff81381f74>] notify_die+0x2e/0x30
[<ffffffff8137f498>] do_general_protection+0x121/0x142
[<ffffffff8137ec04>] ? irq_return+0x0/0xc
[<ffffffff8137ede5>] general_protection+0x25/0x30
[<ffffffff8121de8c>] ? pfn_to_dma_pte+0x73/0x190
[<ffffffff8121df5b>] ? pfn_to_dma_pte+0x142/0x190
[<ffffffff8121dfbe>] intel_iommu_iova_to_phys+0x15/0x2a
[<ffffffff812a9573>] iommu_iova_to_phys+0x13/0x15
[<ffffffffa04e91d0>] kvm_iommu_map_pages+0x77/0x194 [kvm]
[<ffffffff8111404d>] ? __vmalloc_node+0x86/0x9b
[<ffffffffa04e30e2>] __kvm_set_memory_region+0x4e5/0x787 [kvm]
[<ffffffff81081ee8>] ? mark_held_locks+0x50/0x72
[<ffffffff8137c983>] ? mutex_lock_nested+0x325/0x34d
[<ffffffffa04e33bb>] kvm_set_memory_region+0x37/0x50 [kvm]
[<ffffffffa04e4c15>] kvm_vm_ioctl_set_memory_region+0x18/0x1a [kvm]
[<ffffffffa04e4e44>] kvm_vm_ioctl+0x22d/0x3b1 [kvm]
[<ffffffff811355aa>] ? fget_light+0x17b/0x31f
[<ffffffff81143bd7>] do_vfs_ioctl+0x4c6/0x507
[<ffffffff81135732>] ? fget_light+0x303/0x31f
[<ffffffff811355aa>] ? fget_light+0x17b/0x31f
[<ffffffff8137ebb9>] ? retint_swapgs+0x13/0x1b
[<ffffffff81143c6e>] sys_ioctl+0x56/0x7c
[<ffffffff81002df2>] system_call_fastpath+0x16/0x1b

I guess this is not intended to trigger here, specifically as it showed
up first and may be misinterpreted as the core of the issue.

Jan