From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752581Ab2AXO6q (ORCPT ); Tue, 24 Jan 2012 09:58:46 -0500 Received: from rcsinet15.oracle.com ([148.87.113.117]:47116 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750741Ab2AXO6p (ORCPT ); Tue, 24 Jan 2012 09:58:45 -0500 Date: Tue, 24 Jan 2012 09:51:32 -0500 From: Konrad Rzeszutek Wilk To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, benh@kernel.crashing.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, tj@kernel.org, tglx@linutronix.de, mingo@elte.hu Cc: linux-tip-commits@vger.kernel.org Subject: Re: [tip:core/urgent] memblock: Fix alloc failure due to dumb underflow protection in memblock_find_in_range_node () Message-ID: <20120124145132.GA30828@phenom.dumpdata.com> References: <20120113181412.GA11112@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet21.oracle.com [156.151.31.93] X-CT-RefId: str=0001.0A090203.4F1EC70E.013B,ss=1,re=-2.300,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 16, 2012 at 01:03:50AM -0800, tip-bot for Tejun Heo wrote: > Commit-ID: 5d53cb27d849c899136c048ec84c940ac449494b > Gitweb: http://git.kernel.org/tip/5d53cb27d849c899136c048ec84c940ac449494b > Author: Tejun Heo > AuthorDate: Fri, 13 Jan 2012 10:14:12 -0800 > Committer: Ingo Molnar > CommitDate: Mon, 16 Jan 2012 08:38:06 +0100 > > memblock: Fix alloc failure due to dumb underflow protection in memblock_find_in_range_node() > > 7bd0b0f0da ("memblock: Reimplement memblock allocation using > reverse free area iterator") implemented a simple top-down > allocator using a reverse memblock iterator. To avoid underflow > in the allocator loop, it simply raised the lower boundary to > the requested size under the assumption that requested size > would be far smaller than available memblocks. > > This causes early page table allocation failure under certain > configurations in Xen. Fix it by checking for underflow directly > instead of bumping up lower bound. Well, it fixes my 4GB problem, but when I try to boot a 2GB (1GB of that is for balloon usage) guest (i386 only) I get a new failure: > more /mnt/lab/bootstrap-i386/test.xm extra="console=hvc0 debug earlyprintk=xen memblock=debug" kernel="/mnt/lab/bootstrap-i386/vmlinuz" ramdisk="/mnt/lab/bootstrap-i386/initramfs.cpio.gz" memory=1024 maxmem=2048 vcpus=2 name="bootstrap-i386" on_crash="preserve" vif = [ 'mac=00:0F:4B:00:00:68, bridge=switch' ] vfb = [ 'vnc=1, vnclisten=0.0.0.0,vncunused=1'] disk=['phy:/dev/vg_guests/bootstrap-i386,xvda,w'] So this is v3.3-rc1 + this patch by itself. Any thoughts of what else might be amiss? Using config file "/mnt/lab/bootstrap-i386/test.xm". Started domain bootstrap-i386 (id=2) (early) [ 0.000000] Reserving virtual address space above 0xf5800000 (early) [ 0.000000] Initializing cgroup subsys cpuset (early) [ 0.000000] Initializing cgroup subsys cpu (early) [ 0.000000] Linux version 3.3.0-rc1-00065-gc9d7799 (konrad@build.dumpdata.com) (gcc version 4.4.4 20100503 (Red Hat 4.4.4-2) (GCC) ) #1 SMP PREEMPT Tue Jan 24 04:34:24 EST 2012 (early) [ 0.000000] ACPI in unprivileged domain disabled (early) [ 0.000000] Released 0 pages of unused memory (early) [ 0.000000] Set 0 page(s) to 1-1 mapping (early) [ 0.000000] BIOS-provided physical RAM map: (early) [ 0.000000] Xen: 0000000000000000 - 00000000000a0000 (usable) (early) [ 0.000000] Xen: 00000000000a0000 - 0000000000100000 (reserved) (early) [ 0.000000] Xen: 0000000000100000 - 0000000080800000 (usable) (early) [ 0.000000] bootconsole [xenboot0] enabled (early) [ 0.000000] NX (Execute Disable) protection: active (early) [ 0.000000] DMI not present or invalid. (early) [ 0.000000] e820 update range: 0000000000000000 - 0000000000010000 (early) (usable)(early) ==> (early) (reserved)(early) (early) [ 0.000000] e820 remove range: 00000000000a0000 - 0000000000100000 (early) (usable)(early) (early) [ 0.000000] last_pfn = 0x80800 max_arch_pfn = 0x1000000 (early) [ 0.000000] memblock_reserve: [0x0000000185a000-0x0000000186b000] setup_arch+0x67a/0xc9e (early) [ 0.000000] MEMBLOCK configuration: (early) [ 0.000000] memory size = 0x80790000 reserved size = 0x59593000 (early) [ 0.000000] memory.cnt = 0x2 (early) [ 0.000000] memory[0x0] [0x00000000010000-0x0000000009ffff], 0x90000 bytes (early) [ 0.000000] memory[0x1] [0x00000000100000-0x000000807fffff], 0x80700000 bytes (early) [ 0.000000] reserved.cnt = 0x3 (early) [ 0.000000] reserved[0x0] [0x00000001000000-0x0000000186afff], 0x86b000 bytes (early) [ 0.000000] reserved[0x1] [0x00000001ab4000-0x00000019fdbfff], 0x18528000 bytes (early) [ 0.000000] reserved[0x2] [0x00000040000000-0x000000807fffff], 0x40800000 bytes (early) [ 0.000000] initial memory mapped : 0 - 1abff000 (early) [ 0.000000] memblock_reserve: [0x0000000009c000-0x000000000a0000] setup_trampolines+0x81/0xba (early) [ 0.000000] Base memory trampoline at [c009c000] 9c000 size 16384 (early) [ 0.000000] init_memory_mapping: 0000000000000000-000000002d3fe000 (early) [ 0.000000] 0000000000 - 002d3fe000 page 4k (early) [ 0.000000] kernel direct mapping tables up to 2d3fe000 @ 1aa92000-1abff000 (early) [ 0.000000] memblock_reserve: [0x0000001aa92000-0x0000001ab26000] native_pagetable_reserve+0x22/0x28 (early) [ 0.000000] xen: setting RW the range 1ab26000 - 1abff000 (early) [ 0.000000] memblock_free: [0x00000001ab4000-0x00000019e05000] setup_arch+0x7d5/0xc9e (early) [ 0.000000] initrd too large to handle, disabling initrd (early) [ 0.000000] 1332MB HIGHMEM available. (early) [ 0.000000] 723MB LOWMEM available. (early) [ 0.000000] mapped low ram: 0 - 2d3fe000 (early) [ 0.000000] low ram: 0 - 2d3fe000 (early) [ 0.000000] memblock_reserve: [0x0000002d3fd000-0x0000002d3fe000] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] Zone PFN ranges: (early) [ 0.000000] DMA (early) 0x00000010 -> 0x00001000 (early) [ 0.000000] Normal (early) 0x00001000 -> 0x0002d3fe (early) [ 0.000000] HighMem (early) 0x0002d3fe -> 0x00080800 (early) [ 0.000000] Movable zone start PFN for each node (early) [ 0.000000] Early memory PFN ranges (early) [ 0.000000] 0: 0x00000010 -> 0x000000a0 (early) [ 0.000000] 0: 0x00000100 -> 0x00080800 (early) [ 0.000000] On node 0 totalpages: 526224 (early) [ 0.000000] memblock_reserve: [0x0000002c3ed000-0x0000002d3fd000] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] free_area_init_node: node 0, pgdat c170c540, node_mem_map ec3ed200 (early) [ 0.000000] DMA zone: 32 pages used for memmap (early) [ 0.000000] DMA zone: 0 pages reserved (early) [ 0.000000] DMA zone: 3952 pages, LIFO batch:0 (early) [ 0.000000] memblock_reserve: [0x0000002c3ecfc0-0x0000002c3ecfc4] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3ecf00-0x0000002c3ecfc0] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] Normal zone: 1416 pages used for memmap (early) [ 0.000000] Normal zone: 179830 pages, LIFO batch:31 (early) [ 0.000000] memblock_reserve: [0x0000002c3ece40-0x0000002c3ecec8] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e9e40-0x0000002c3ece40] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] HighMem zone: 2665 pages used for memmap (early) [ 0.000000] HighMem zone: 338329 pages, LIFO batch:31 (early) [ 0.000000] memblock_reserve: [0x0000002c3e9d40-0x0000002c3e9e3c] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e3d40-0x0000002c3e9d40] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] Using APIC driver default (early) [ 0.000000] SMP: Allowing 2 CPUs, 0 hotplug CPUs (early) [ 0.000000] Local APIC disabled by BIOS -- you can enable it with "lapic" (early) [ 0.000000] APIC: disable apic facility (early) [ 0.000000] APIC: switched to apic NOOP (early) [ 0.000000] nr_irqs_gsi: 16 (early) [ 0.000000] memblock_reserve: [0x0000002c3e3c80-0x0000002c3e3d10] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e3c40-0x0000002c3e3c80] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e3c00-0x0000002c3e3c40] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e3bc0-0x0000002c3e3c00] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e3b80-0x0000002c3e3b90] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] PM: Registered nosave memory: 00000000000a0000 - 0000000000100000 (early) [ 0.000000] Allocating PCI resources starting at 80800000 (gap: 80800000:7f800000) (early) [ 0.000000] Booting paravirtualized kernel on Xen (early) [ 0.000000] Xen version: 4.1-120124 (preserve-AD) (early) [ 0.000000] memblock_reserve: [0x0000002c3e3b40-0x0000002c3e3b72] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e3b00-0x0000002c3e3b32] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] setup_percpu: NR_CPUS:8 nr_cpumask_bits:8 nr_cpu_ids:2 nr_node_ids:1 (early) [ 0.000000] memblock_reserve: [0x0000002c3e2b00-0x0000002c3e3b00] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e1b00-0x0000002c3e2b00] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3c5000-0x0000002c3e1000] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_free: [0x0000002c3d3000-0x0000002c3d3000] free_bootmem+0x2b/0x31 (early) [ 0.000000] memblock_free: [0x0000002c3e1000-0x0000002c3e1000] free_bootmem+0x2b/0x31 (early) [ 0.000000] PERCPU: Embedded 14 pages/cpu @ec3c5000 s33600 r0 d23744 u57344 (early) [ 0.000000] memblock_reserve: [0x0000002c3e1ac0-0x0000002c3e1ac4] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e1a80-0x0000002c3e1a84] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e1a40-0x0000002c3e1a48] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e1a00-0x0000002c3e1a08] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] pcpu-alloc: s33600 r0 d23744 u57344 alloc=14*4096(early) (early) [ 0.000000] pcpu-alloc: (early) [0] (early) 0 (early) [0] (early) 1 (early) (early) [ 0.000000] memblock_reserve: [0x0000002c3e1980-0x0000002c3e19f8] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_reserve: [0x0000002c3e1940-0x0000002c3e196c] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] memblock_free: [0x0000002c3e2b00-0x0000002c3e3b00] free_bootmem+0x2b/0x31 (early) [ 0.000000] memblock_free: [0x0000002c3e1b00-0x0000002c3e2b00] free_bootmem+0x2b/0x31 (early) [ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 522111 (early) [ 0.000000] Kernel command line: console=hvc0 debug earlyprintk=xen memblock=debug (early) [ 0.000000] memblock_reserve: [0x0000002c3c1000-0x0000002c3c5000] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] PID hash table entries: 4096 (order: 2, 16384 bytes) (early) [ 0.000000] memblock_reserve: [0x0000002c341000-0x0000002c3c1000] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes) (early) [ 0.000000] memblock_reserve: [0x0000002c301000-0x0000002c341000] __alloc_memory_core_early+0x8c/0xaa (early) [ 0.000000] Inode-cache hash table entries: 65536 (order: 6, 262144 bytes) (early) [ 0.000000] Initializing CPU#0 (early) [ 0.000000] Initializing HighMem for node 0 (0002d3fe:00080800) (early) [ 0.000000] Memory: 1019624k/2105344k available (5450k kernel code, 28504k reserved, 1812k data, 508k init, 307208k highmem) (early) [ 0.000000] virtual kernel memory layout: (early) [ 0.000000] fixmap : 0xf5715000 - 0xf57ff000 ( 936 kB) (early) [ 0.000000] pkmap : 0xf5400000 - 0xf5600000 (2048 kB) (early) [ 0.000000] vmalloc : 0xedbfe000 - 0xf53fe000 ( 120 MB) (early) [ 0.000000] lowmem : 0xc0000000 - 0xed3fe000 ( 723 MB) (early) [ 0.000000] .init : 0xc1718000 - 0xc1797000 ( 508 kB) (early) [ 0.000000] .data : 0xc1552935 - 0xc1717a40 (1812 kB) (early) [ 0.000000] .text : 0xc1000000 - 0xc1552935 (5450 kB) (early) [ 0.000000] SLUB: Genslabs=15, HWalign=64, Order=0-3, MinObjects=0, CPUs=2, Nodes=1 (early) [ 0.000000] Preemptible hierarchical RCU implementation. (early) [ 0.000000] NR_IRQS:2304 nr_irqs:288 16 (early) [ 0.000000] CPU 0 irqstacks, hard=ebc10000 soft=ebc12000 (early) [ 0.000000] Console: colour dummy device 80x25 (early) [ 0.000000] console [tty0] enabled [ 0.000000] console [hvc0] enabled, bootconsole disabled (early) [ 0.000000] console [hvc0] enabled, bootconsole disabled [ 0.000000] Xen: using vcpuop timer interface [ 0.000000] installing Xen timer for CPU 0 [ 0.000000] Detected 3292.620 MHz processor. [ 0.000999] Calibrating delay loop (skipped), value calculated using timer frequency.. 6585.24 BogoMIPS (lpj=3292620) [ 0.000999] pid_max: default: 32768 minimum: 301 [ 0.000999] Security Framework initialized [ 0.000999] SELinux: Initializing. [ 0.000999] SELinux: Starting in permissive mode [ 0.000999] Mount-cache hash table entries: 512 [ 0.001120] Initializing cgroup subsys cpuacct [ 0.001130] Initializing cgroup subsys freezer [ 0.001263] CPU: Physical Processor ID: 0 [ 0.001272] CPU: Processor Core ID: 0 [ 0.001280] ENERGY_PERF_BIAS: Set to 'normal', was 'performance' [ 0.001281] ENERGY_PERF_BIAS: View and update with x86_energy_perf_policy(8) [ 0.001519] SMP alternatives: switching to UP code [ 0.002138] cpu 0 spinlock event irq 17 [ 0.002298] Performance Events: unsupported p6 CPU model 42 no PMU driver, software events only. [ 0.008072] NMI watchdog disabled (cpu0): hardware events not enabled [ 0.014031] CPU 1 irqstacks, hard=ebc8a000 soft=ebc8c000 [ 0.014041] installing Xen timer for CPU 1 [ 0.014116] cpu 1 spinlock event irq 23 [ 0.014145] SMP alternatives: switching to SMP code [ 0.000999] Initializing CPU#1 [ 0.000999] Disabled fast string operations [ 0.015199] NMI watchdog disabled (cpu1): hardware events not enabled [ 0.017015] Brought up 2 CPUs [ 0.019112] kworker/u:0 used greatest stack depth: 6968 bytes left [ 0.019157] Grant tables using version 2 layout. [ 0.019157] Grant table initialized [ 0.038273] RTC time: 165:165:165, date: 165/165/65 [ 0.038580] NET: Registered protocol family 16 [ 0.041681] PCI: setting up Xen PCI frontend stub [ 0.041691] PCI: pci_cache_line_size set to 64 bytes [ 0.043149] kworker/u:0 used greatest stack depth: 6928 bytes left [ 0.046216] kworker/u:0 used greatest stack depth: 6784 bytes left [ 0.067350] kworker/u:0 used greatest stack depth: 6620 bytes left [ 0.086154] bio: create slab at 0 [ 0.087533] ACPI: Interpreter disabled. [ 0.087647] xen/balloon: Initialising balloon driver. [ 0.092191] xen-balloon: Initialising balloon driver. [ 0.093348] vgaarb: loaded [ 0.095177] usbcore: registered new interface driver usbfs [ 0.095274] usbcore: registered new interface driver hub [ 0.096014] usbcore: registered new device driver usb [ 0.097187] PCI: System does not support PCI [ 0.097187] PCI: System does not support PCI [ 0.098239] NetLabel: Initializing [ 0.098239] NetLabel: domain hash size = 128 [ 0.098239] NetLabel: protocols = UNLABELED CIPSOv4 [ 0.098274] NetLabel: unlabeled traffic allowed by default [ 0.099464] Switching to clocksource xen [ 0.130294] pnp: PnP ACPI: disabled [ 0.156747] PCI: max bus depth: 0 pci_try_num: 1 [ 0.156899] NET: Registered protocol family 2 [ 0.157124] IP route cache hash table entries: 32768 (order: 5, 131072 bytes) [ 0.157918] TCP established hash table entries: 131072 (order: 8, 1048576 bytes) [ 0.158302] TCP bind hash table entries: 65536 (order: 7, 524288 bytes) [ 0.158391] TCP: Hash tables configured (established 131072 bind 65536) [ 0.158402] TCP reno registered [ 0.158414] UDP hash table entries: 512 (order: 2, 16384 bytes) [ 0.158429] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes) [ 0.158763] NET: Registered protocol family 1 [ 0.159684] RPC: Registered named UNIX socket transport module. [ 0.159696] RPC: Registered udp transport module. [ 0.159704] RPC: Registered tcp transport module. [ 0.159712] RPC: Registered tcp NFSv4.1 backchannel transport module. [ 0.159723] PCI: CLS 0 bytes, default 64 [ 0.249509] DMA-API: preallocated 32768 debug entries [ 0.249524] DMA-API: debugging enabled by kernel config [ 0.250058] platform rtc_cmos: registered platform RTC device (no PNP device found) [ 0.250596] Machine check injector initialized [ 0.252469] microcode: no support for this CPU vendor [ 0.254141] audit: initializing netlink socket (disabled) [ 0.254196] type=2000 audit(1327444216.488:1): initialized [ 0.267418] highmem bounce pool size: 64 pages [ 0.267441] HugeTLB registered 2 MB page size, pre-allocated 0 pages [ 0.291085] kworker/u:0 used greatest stack depth: 6588 bytes left [ 0.293529] VFS: Disk quotas dquot_6.5.2 [ 0.294081] Dquot-cache hash table entries: 1024 (order 0, 4096 bytes) [ 0.297116] NTFS driver 2.1.30 [Flags: R/W]. [ 0.298412] msgmni has been set to 1391 [ 0.299046] SELinux: Registering netfilter hooks [ 0.301611] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253) [ 0.301625] io scheduler noop registered [ 0.301633] io scheduler deadline registered [ 0.301663] io scheduler cfq registered (default) [ 0.302462] pci_hotplug: PCI Hot Plug PCI Core version: 0.5 [ 0.400113] kworker/u:1 used greatest stack depth: 6496 bytes left [ 0.461905] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled [ 0.484000] Non-volatile memory driver v1.3 [ 0.484022] Linux agpgart interface v0.103 [ 0.487010] [drm] Initialized drm 1.1.0 20060810 [ 0.502366] brd: module loaded [ 0.510758] loop: module loaded [ 0.512577] Fixed MDIO Bus: probed [ 0.512587] tun: Universal TUN/TAP device driver, 1.6 [ 0.512595] tun: (C) 1999-2004 Max Krasnyansky [ 0.514744] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver [ 0.514756] ehci_hcd: block sizes: qh 68 qtd 96 itd 160 sitd 96 [ 0.515062] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver [ 0.515073] ohci_hcd: block sizes: ed 64 td 64 [ 0.515319] uhci_hcd: USB Universal Host Controller Interface driver [ 0.515892] usbcore: registered new interface driver usblp [ 0.516182] usbcore: registered new interface driver libusual [ 0.516986] i8042: PNP: No PS/2 controller found. Probing ports directly. [ 0.517812] i8042: No controller found [ 0.518502] mousedev: PS/2 mouse device common for all mice [ 0.560132] rtc_cmos rtc_cmos: rtc core: registered rtc_cmos as rtc0 [ 0.560440] rtc_cmos: probe of rtc_cmos failed with error -38 [ 0.561343] EFI Variables Facility v0.08 2004-May-17 [ 0.562715] Netfilter messages via NETLINK v0.30. [ 0.562771] nf_conntrack version 0.5.0 (15931 buckets, 63724 max) [ 0.563857] ctnetlink v0.93: registering with nfnetlink. [ 0.565724] ip_tables: (C) 2000-2006 Netfilter Core Team [ 0.565930] TCP cubic registered [ 0.565938] Initializing XFRM netlink socket [ 0.567531] NET: Registered protocol family 10 [ 0.570396] ip6_tables: (C) 2000-2006 Netfilter Core Team [ 0.570615] IPv6 over IPv4 tunneling driver [ 0.573725] NET: Registered protocol family 17 [ 0.573841] Registering the dns_resolver key type [ 0.573932] Using IPI No-Shortcut mode [ 0.574835] PM: Hibernation image not present or could not be loaded. [ 0.574914] registered taskstats version 1 [ 0.575042] kmemleak: Kernel memory leak detector initialized [ 0.575065] kmemleak: Automatic memory scanning thread started [ 0.575189] XENBUS: Device with no driver: device/vkbd/0 [ 0.575199] XENBUS: Device with no driver: device/vfb/0 [ 0.575208] XENBUS: Device with no driver: device/vbd/51712 [ 0.575216] XENBUS: Device with no driver: device/vif/0 [ 0.575225] XENBUS: Device with no driver: device/console/0 [ 0.575248] Magic number: 1:252:3141 [ 0.576109] Root-NFS: no NFS server address [ 0.576118] VFS: Unable to mount root fs via NFS, trying floppy. [ 0.576215] VFS: Cannot open root device "(null)" or unknown-block(2,0) [ 0.576224] Please append a correct "root=" boot option; here are the available partitions: [ 0.576244] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)