Your BIOS is broken とかいわれていた件
/var/log/messages に次のような警告が出ていたのを放置したままでいたので、対処法を調べてみた。
------------[ cut here ]------------ WARNING: at drivers/pci/intel-iommu.c:3808 init_dmars+0x359/0x6e1() Hardware name: System Product Name Your BIOS is broken; DMA routed to ISOCH DMAR unit but no TLB space. BIOS vendor: American Megatrends Inc.; Ver: 0504 ; Product Version: System Version Modules linked in: Pid: 1, comm: swapper Not tainted 2.6.35.7-1m.mo7.x86_64 #1 Call Trace: [<ffffffff81049df7>] warn_slowpath_common+0x80/0x98 [<ffffffff81049ea3>] warn_slowpath_fmt+0x41/0x43 [<ffffffff8188c658>] init_dmars+0x359/0x6e1 [<ffffffff8188cc68>] intel_iommu_init+0x288/0x37e [<ffffffff818663fe>] ? pci_iommu_init+0x0/0x31 [<ffffffff81866408>] pci_iommu_init+0xa/0x31 [<ffffffff8100205f>] do_one_initcall+0x59/0x154 [<ffffffff8185f7b7>] kernel_init+0x227/0x2b5 [<ffffffff810098e4>] kernel_thread_helper+0x4/0x10 [<ffffffff8185f590>] ? kernel_init+0x0/0x2b5 [<ffffffff810098e0>] ? kernel_thread_helper+0x0/0x10 ---[ end trace d9d3a1889f8925bd ]---