aboutsummaryrefslogtreecommitdiff
path: root/arch
AgeCommit message (Collapse)Author
2008-01-30[SCSI] remove use_sg_chainingJames Bottomley
With the sg table code, every SCSI driver is now either chain capable or broken (or has sg_tablesize set so chaining is never activated), so there's no need to have a check in the host template. Also tidy up the code by moving the scatterlist size defines into the SCSI includes and permit the last entry of the scatterlist pools not to be a power of two. Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
2008-01-30KVM: Move apic timer migration away from critical sectionAvi Kivity
Migrating the apic timer in the critical section is not very nice, and is absolutely horrible with the real-time port. Move migration to the regular vcpu execution path, triggered by a new bitflag. Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Fix unbounded preemption latencyAvi Kivity
When preparing to enter the guest, if an interrupt comes in while preemption is disabled but interrupts are still enabled, we miss a preemption point. Fix by explicitly checking whether we need to reschedule. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Initialize the mmu caches only after verifying cpu supportAvi Kivity
Otherwise we re-initialize the mmu caches, which will fail since the caches are already registered, which will cause us to deinitialize said caches. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Fix dirty page setting for pages removed from rmapIzik Eidus
Right now rmap_remove won't set the page as dirty if the shadow pte pointed to this page had write access and then it became readonly. This patches fixes that, by setting the page as dirty for spte changes from write to readonly access. Signed-off-by: Izik Eidus <izike@qumranet.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: x86 emulator: Only allow VMCALL/VMMCALL trapped by #UDSheng Yang
When executing a test program called "crashme", we found the KVM guest cannot survive more than ten seconds, then encounterd kernel panic. The basic concept of "crashme" is generating random assembly code and trying to execute it. After some fixes on emulator insn validity judgment, we found it's hard to get the current emulator handle the invalid instructions correctly, for the #UD trap for hypercall patching caused troubles. The problem is, if the opcode itself was OK, but combination of opcode and modrm_reg was invalid, and one operand of the opcode was memory (SrcMem or DstMem), the emulator will fetch the memory operand first rather than checking the validity, and may encounter an error there. For example, ".byte 0xfe, 0x34, 0xcd" has this problem. In the patch, we simply check that if the invalid opcode wasn't vmcall/vmmcall, then return from emulate_instruction() and inject a #UD to guest. With the patch, the guest had been running for more than 12 hours. Signed-off-by: Feng (Eric) Liu <eric.e.liu@intel.com> Signed-off-by: Sheng Yang <sheng.yang@intel.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Merge shadow level check in FNAME(fetch)Dong, Eddie
Remove the redundant level check when fetching shadow pte for present & non-present spte. Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Move kvm_free_some_pages() into critical sectionAvi Kivity
If some other cpu steals mmu pages between our check and an attempt to allocate, we can run out of mmu pages. Fix by moving the check into the same critical section as the allocation. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Switch to mmu spinlockMarcelo Tosatti
Convert the synchronization of the shadow handling to a separate mmu_lock spinlock. Also guard fetch() by mmap_sem in read-mode to protect against alias and memslot changes. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Avoid calling gfn_to_page() in mmu_set_spte()Avi Kivity
Since gfn_to_page() is a sleeping function, and we want to make the core mmu spinlocked, we need to pass the page from the walker context (which can sleep) to the shadow context (which cannot). [marcelo: avoid recursive locking of mmap_sem] Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Add kvm_read_guest_atomic()Marcelo Tosatti
In preparation for a mmu spinlock, add kvm_read_guest_atomic() and use it in fetch() and prefetch_page(). Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Concurrent guest walkersMarcelo Tosatti
Do not hold kvm->lock mutex across the entire pagefault code, only acquire it in places where it is necessary, such as mmu hash list, active list, rmap and parent pte handling. Allow concurrent guest walkers by switching walk_addr() to use mmap_sem in read-mode. And get rid of the lockless __gfn_to_page. [avi: move kvm_mmu_pte_write() locking inside the function] [avi: add locking for real mode] [avi: fix cmpxchg locking] Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Disable vapic support on Intel machines with FlexPriorityAvi Kivity
FlexPriority accelerates the tpr without any patching. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Accelerated apic supportAvi Kivity
This adds a mechanism for exposing the virtual apic tpr to the guest, and a protocol for letting the guest update the tpr without causing a vmexit if conditions allow (e.g. there is no interrupt pending with a higher priority than the new tpr). Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: local APIC TPR access reporting facilityAvi Kivity
Add a facility to report on accesses to the local apic tpr even if the local apic is emulated in the kernel. This is basically a hack that allows userspace to patch Windows which tends to bang on the tpr a lot. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Print data for unimplemented wrmsrAvi Kivity
This can help diagnosing what the guest is trying to do. In many cases we can get away with partial emulation of msrs. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Add cache miss statisticAvi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: MMU: Coalesce remote tlb flushesEddie Dong
Host side TLB flush can be merged together if multiple spte need to be write-protected. Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Move kvm_vcpu_kick() to x86.cZhang Xiantao
Moving kvm_vcpu_kick() to x86.c. Since it should be common for all archs, put its declarations in <linux/kvm_host.h> Signed-off-by: Zhang Xiantao <xiantao.zhang@intel.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Move ioapic code to common directory.Zhang Xiantao
Move ioapic code to common, since IA64 also needs it. Signed-off-by: Zhang Xiantao <xiantao.zhang@intel.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Move irqchip declarations into new ioapic.h and lapic.hZhang Xiantao
This allows reuse of ioapic in ia64. Signed-off-by: Zhang Xiantao <xiantao.zhang@intel.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Move drivers/kvm/* to virt/kvm/Avi Kivity
Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Move arch dependent files to new directory arch/x86/kvm/Avi Kivity
This paves the way for multiple architecture support. Note that while ioapic.c could potentially be shared with ia64, it is also moved. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30KVM: Export include/linux/kvm.h only if $ARCH actually supports KVMAvi Kivity
Currently, make headers_check barfs due to <asm/kvm.h>, which <linux/kvm.h> includes, not existing. Rather than add a zillion <asm/kvm.h>s, export kvm.h only if the arch actually supports it. Signed-off-by: Avi Kivity <avi@qumranet.com>
2008-01-30x86: fix nodemap_size according to nodeid bitsYinghai Lu
memnode.map is s16 array because of nodeid is 16 bit now. so need to increase the nodemap_size according to that bits. Signed-off-by: Yinghai Lu <yinghai.lu@sun.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: fix overlap between pagetable with bss sectionYinghai Lu
one early crash on one 8 node 256g machine: Command line: console=uart8250,io,0x3f8,115200n8 initrd=kernel.org/mydisk11_x86_64.gz rw root=/dev/ram0 debug initcall_debug apic=debug acpi.debug_level=0x0000000f pci=routeirq ip=dhcp load_ramdisk=1 ramdisk_size=131072 BOOT_IMAGE=kernel.org/bzImage_2.6.25_k8.1 BIOS-provided physical RAM map: BIOS-e820: 0000000000000000 - 000000000009bc00 (usable) BIOS-e820: 000000000009bc00 - 00000000000a0000 (reserved) BIOS-e820: 00000000000e6000 - 0000000000100000 (reserved) BIOS-e820: 0000000000100000 - 00000000dffe0000 (usable) BIOS-e820: 00000000dffe0000 - 00000000dffee000 (ACPI data) BIOS-e820: 00000000dffee000 - 00000000dffff050 (ACPI NVS) BIOS-e820: 00000000dffff050 - 00000000e0000000 (reserved) BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved) BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved) BIOS-e820: 00000000ff700000 - 0000000100000000 (reserved) BIOS-e820: 0000000100000000 - 0000004020000000 (usable) Early serial console at I/O port 0x3f8 (options '115200n8') console [uart0] enabled end_pfn_map = 67239936 Kernel panic - not syncing: Duplicated early reservation d40000-e42000 Pid: 0, comm: swapper Not tainted 2.6.24-smp-g5a514e21-dirty #3 Call Trace: [<ffffffff80221545>] lapic_get_maxlvt+0x0/0x10 [<ffffffff80221657>] clear_local_APIC+0x5/0xcf [<ffffffff80221726>] disable_local_APIC+0x5/0x17 [<ffffffff8021fe16>] smp_send_stop+0x46/0x4c [<ffffffff80235293>] panic+0x94/0x13e [<ffffffff80bc3b03>] sctp_eps_proc_init+0x12/0x34 [<ffffffff80b9f1c5>] reserve_early+0x30/0x6c [<ffffffff80803925>] init_memory_mapping+0x2cd/0x2dc [<ffffffff80b9dc01>] setup_arch+0x21f/0x44e [<ffffffff80b978be>] start_kernel+0x6f/0x2c7 [<ffffffff80b971cc>] _sinittext+0x1cc/0x1d3 it turns out there is overlap between pgtable and bss... in System.map we have ffffffff80d40420 b rsi_table ffffffff80d40620 B krb5_seq_lock ffffffff80d40628 b i.20437 ffffffff80d40630 b xprt_rdma_inline_write_padding ffffffff80d40638 b sunrpc_table_header ffffffff80d40640 b zero ffffffff80d40644 b min_memreg ffffffff80d40648 b rpcrdma_tk_lock_g ffffffff80d40650 B sctp_assocs_id_lock ffffffff80d40658 B proc_net_sctp ffffffff80d40660 B sctp_assocs_id ffffffff80d40680 B sysctl_sctp_mem ffffffff80d40690 B sysctl_sctp_rmem ffffffff80d406a0 B sysctl_sctp_wmem ffffffff80d406b0 b sctp_ctl_socket ffffffff80d406b8 b sctp_pf_inet6_specific ffffffff80d406c0 b sctp_pf_inet_specific ffffffff80d406c8 b sctp_af_v4_specific ffffffff80d406d0 b sctp_af_v6_specific ffffffff80d406d8 b sctp_rand.33270 ffffffff80d406dc b sctp_memory_pressure ffffffff80d406e0 b sctp_sockets_allocated ffffffff80d406e4 b sctp_memory_allocated ffffffff80d406e8 b sctp_sysctl_header ffffffff80d406f0 b zero ffffffff80d406f4 A __bss_stop ffffffff80d406f4 A _end need to round up table_start to PAGE_SIZE. also make the panic more informative. Signed-off-by: Yinghai Lu <yinghai.lu@sun.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: add PCI IDs to k8topology_64.cJoachim Deguara
This just adds the PCI IDs of AMD's family 10h and 11h CPU's northbridges to k8topology discovery. Signed-off-by: Joachim Deguara <joachim.deguara@amd.com> Signed-off-by: Andi Kleen <ak@suse.de> Acked-by: Yinghai Lu <yinghai.lu@sun.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: fix early_ioremap pagetable opsJeremy Fitzhardinge
Put appropriate pagetable update hooks in so that paravirt knows what's going on in there. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: use the same pgd_list for PAE and 64-bitJeremy Fitzhardinge
Use a standard list threaded through page->lru for maintaining the pgd list on PAE. This is the same as 64-bit, and seems saner than using a non-standard list via page->index. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: early boot debugging via FireWire (ohci1394_dma=early)Bernhard Kaindl
This patch adds a new configuration option, which adds support for a new early_param which gets checked in arch/x86/kernel/setup_{32,64}.c:setup_arch() to decide wether OHCI-1394 FireWire controllers should be initialized and enabled for physical DMA access to allow remote debugging of early problems like issues ACPI or other subsystems which are executed very early. If the config option is not enabled, no code is changed, and if the boot paramenter is not given, no new code is executed, and independent of that, all new code is freed after boot, so the config option can be even enabled in standard, non-debug kernels. With specialized tools, it is then possible to get debugging information from machines which have no serial ports (notebooks) such as the printk buffer contents, or any data which can be referenced from global pointers, if it is stored below the 4GB limit and even memory dumps of of the physical RAM region below the 4GB limit can be taken without any cooperation from the CPU of the host, so the machine can be crashed early, it does not matter. In the extreme, even kernel debuggers can be accessed in this way. I wrote a small kgdb module and an accompanying gdb stub for FireWire which allows to gdb to talk to kgdb using remote remory reads and writes over FireWire. An version of the gdb stub fore FireWire is able to read all global data from a system which is running a a normal kernel without any kernel debugger, without any interruption or support of the system's CPU. That way, e.g. the task struct and so on can be read and even manipulated when the physical DMA access is granted. A HOWTO is included in this patch, in Documentation/debugging-via-ohci1394.txt and I've put a copy online at ftp://ftp.suse.de/private/bk/firewire/docs/debugging-via-ohci1394.txt It also has links to all the tools which are available to make use of it another copy of it is online at: ftp://ftp.suse.de/private/bk/firewire/kernel/ohci1394_dma_early-v2.diff Signed-Off-By: Bernhard Kaindl <bk@suse.de> Tested-By: Thomas Renninger <trenn@suse.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: don't special-case pmd allocations as muchJeremy Fitzhardinge
In x86 PAE mode, stop treating pmds as a special case. Previously they were always allocated and freed with the pgd. The modifies the code to be the same as 64-bit mode, where they are allocated on demand. This is a step on the way to unifying 32/64-bit pagetable allocation as much as possible. There is a complicating wart, however. When you install a new reference to a pmd in the pgd, the processor isn't guaranteed to see it unless you reload cr3. Since reloading cr3 also has the side-effect of flushing the tlb, this is an expense that we want to avoid whereever possible. This patch simply avoids reloading cr3 unless the update is to the current pagetable. Later patches will optimise this further. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Andi Kleen <ak@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: William Irwin <wli@holomorphy.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: shrink some ifdefs in fault.cHarvey Harrison
The change from current to tsk in do_page_fault is safe as this is set at the very beginning of the function. Removes a likely() annotation from the 64-bit version, this could have instead been added to 32-bit. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: ignore spurious faultsJeremy Fitzhardinge
When changing a kernel page from RO->RW, it's OK to leave stale TLB entries around, since doing a global flush is expensive and they pose no security problem. They can, however, generate a spurious fault, which we should catch and simply return from (which will have the side-effect of reloading the TLB to the current PTE). This can occur when running under Xen, because it frequently changes kernel pages from RW->RO->RW to implement Xen's pagetable semantics. It could also occur when using CONFIG_DEBUG_PAGEALLOC, since it avoids doing a global TLB flush after changing page permissions. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: remove nx_enabled from fault.cHarvey Harrison
On !PAE 32-bit, _PAGE_NX will be 0, making is_prefetch always return early. The test is sufficient on PAE as __supported_pte_mask is updated in the same places as nx_enabled in init_32.c which also takes disable_nx into account. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify fault_32|64.cHarvey Harrison
Unify includes in moved fault.c. Modify Makefiles to pick up unified file. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify fault_32|64.c with ifdefsHarvey Harrison
Elimination of these ifdefs can be done in a unified file. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify fault_32|64.c by ifdef'd function bodiesHarvey Harrison
It's about time to get on with unifying these files, elimination of the ugly ifdefs can occur in the unified file. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: arch/x86/mm/init_32.c printk fixesIngo Molnar
printk fixes. NOP in terms of functionality, but strings got a bit larger due to the KERN_ markers that were added. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: arch/x86/mm/init_32.c cleanupIngo Molnar
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: arch/x86/mm/init_64.c printk fixesIngo Molnar
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify ioremapThomas Gleixner
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: fixes some bugs about EFI memory map handlingHuang, Ying
This patch fixes some bugs of EFI memory handing code. - On x86_64, it is possible that EFI memory map can not be mapped via identity map, so efi_map_memmap is removed, just use early_ioremap. - On i386, the EFI memory map mapping take effect cross paging_init, so it is not necessary to use efi_map_memmap. - EFI memory map is unmapped in efi_enter_virtual_mode to avoid early_ioremap leak. Signed-off-by: Huang Ying <ying.huang@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: use reboot_type on EFI 32Huang, Ying
This patch makes reboot_type of BOOT_EFI is used on i386 too. Because correpsonding reboot code of i386 and x86_64 is merged. Signed-off-by: Huang Ying <ying.huang@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify page fault oops printingHarvey Harrison
This changes the oops dumping format for page faults to be similar between X86_32 and 64. This is the first user of printk_address on X86_32. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: introduce show_fault_oops helper to fault_32|64.cHarvey Harrison
This will help when unifying the oops dumping code on 32/64 bit. No functional changes. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: add is_errata100 helper to fault_32|64.cHarvey Harrison
Further towards unifying these files, add another helper in same spirit as is_errata93. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: add is_f00f_bug helper to fault_32|64.cHarvey Harrison
Further towards unifying these files, add another helper in same spirit as is_errata93. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: cpa cleanup the 64-bit alias mathThomas Gleixner
Cleanup the address calculations, which are necessary to identify the high/low alias mappings of the kernel on 64 bit machines. Instead of calling __pa/__va back and forth, calculate the physical address once and base the other calculations on it. Add understandable constants so we can use the already available within() helper. Also add comments, which help mere mortals to understand what this code does. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-01-30x86: cpa: fix the self-testIngo Molnar
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: rodata config hookupIngo Molnar
Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>