1. 25 8月, 2008 2 次提交
    • Y
      x86: fix HPET regression in 2.6.26 versus 2.6.25, check hpet against BAR, v3 · a2bd7274
      Yinghai Lu 提交于
      David Witbrodt tracked down (and bisected) a hpet bootup hang on his
      system to the following problem: a BIOS bug made the hpet device
      visible as a generic PCI device. If e820 reserved entries happen to
      be registered first in the resource tree [which v2.6.26 started doing],
      then the PCI code will reallocate that device's BAR to some other
      address - breaking timer IRQs and hanging the system.
      
      ( Normally hpet devices are hidden by the BIOS from the OS's PCI
        discovery via chipset magic. Sometimes the hpet is not a PCI device
        at all. )
      
      Solve this fundamental fragility by making non-PCI platform drivers
      insert resources into the resource tree even if it overlaps the e820
      reserved entry, to keep the resource manager from updating the BAR.
      
      Also do these checks for the ioapic and mmconfig addresses, and emit
      a warning if this happens.
      Bisected-by: NDavid Witbrodt <dawitbro@sbcglobal.net>
      Signed-off-by: NYinghai Lu <yhlu.kernel@gmail.com>
      Tested-by: NDavid Witbrodt <dawitbro@sbcglobal.net>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      a2bd7274
    • L
      x86: do not enable TSC notifier if we don't need it · 060700b5
      Linus Torvalds 提交于
      Impact: crash on non-TSC-equipped CPUs
      
      Don't enable the TSC notifier if we *either*:
      
      1. don't have a CPU, or
      2. have a CPU with constant TSC.
      
      In either of those cases, the notifier is either damaging (1) or useless(2).
      
      From: Linus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      060700b5
  2. 23 8月, 2008 3 次提交
    • R
      x86 MCE: Fix CPU hotplug problem with multiple multicore AMD CPUs · 8735728e
      Rafael J. Wysocki 提交于
      During CPU hot-remove the sysfs directory created by
      threshold_create_bank(), defined in
      arch/x86/kernel/cpu/mcheck/mce_amd_64.c, has to be removed before
      its parent directory, created by mce_create_device(), defined in
      arch/x86/kernel/cpu/mcheck/mce_64.c .  Moreover, when the CPU in
      question is hotplugged again, obviously the latter has to be created
      before the former.  At present, the right ordering is not enforced,
      because all of these operations are carried out by CPU hotplug
      notifiers which are not appropriately ordered with respect to each
      other.  This leads to serious problems on systems with two or more
      multicore AMD CPUs, among other things during suspend and hibernation.
      
      Fix the problem by placing threshold bank CPU hotplug callbacks in
      mce_cpu_callback(), so that they are invoked at the right places,
      if defined.  Additionally, use kobject_del() to remove the sysfs
      directory associated with the kobject created by
      kobject_create_and_add() in threshold_create_bank(), to prevent the
      kernel from crashing during CPU hotplug operations on systems with
      two or more multicore AMD CPUs.
      
      This patch fixes bug #11337.
      Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>
      Acked-by: NAndi Kleen <andi@firstfloor.org>
      Tested-by: NMark Langsdorf <mark.langsdorf@amd.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      8735728e
    • R
      x86: fix: make PCI ECS for AMD CPUs hotplug capable · 91ede005
      Robert Richter 提交于
      Until now, PCI ECS setup was performed at boot time only and for cpus
      that are enabled then. This patch fixes this and adds cpu hotplug.
      
      Tests sequence (check if ECS bit is set when bringing cpu online again):
      
       # ( perl -e 'sysseek(STDIN, 0xC001001F, 0)'; hexdump -n 8 -e '2/4 "%08x " "\n"' )   < /dev/cpu/1/msr
       00000008 00404010
       # ( perl -e 'sysseek(STDOUT, 0xC001001F, 0); print pack "l*", 8, 0x00400010' ) > /dev/cpu/1/msr
       # ( perl -e 'sysseek(STDIN, 0xC001001F, 0)'; hexdump -n 8 -e '2/4 "%08x " "\n"' )   < /dev/cpu/1/msr
       00000008 00400010
       # echo 0 > /sys/devices/system/cpu/cpu1/online
       # echo 1 > /sys/devices/system/cpu/cpu1/online
       # ( perl -e 'sysseek(STDIN, 0xC001001F, 0)'; hexdump -n 8 -e '2/4 "%08x " "\n"' )   < /dev/cpu/1/msr
       00000008 00404010
      Reported-by: NYinghai Lu <yhlu.kernel@gmail.com>
      Signed-off-by: NRobert Richter <robert.richter@amd.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      91ede005
    • R
      x86: fix: do not run code in amd_bus.c on non-AMD CPUs · 9b4e27b5
      Robert Richter 提交于
      Jan Beulich wrote:
      
      > Even worse - this would even try to access the MSR on non-AMD CPUs
      > (currently probably prevented just by the fact that only AMD ones use
      > family values of 0x10 or higher).
      
      This patch adds cpu vendor check to the postcore_initcalls.
      Reported-by: NJan Beulich <jbeulich@novell.com>
      Signed-off-by: NRobert Richter <robert.richter@amd.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      9b4e27b5
  3. 22 8月, 2008 6 次提交
    • I
      x86: work around MTRR mask setting, v2 · 9754a5b8
      Ingo Molnar 提交于
      improve the debug printout:
      
      - make it actually display something
      - print it only once
      
      would be nice to have a WARN_ONCE() facility, to feed such things to
      kerneloops.org.
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      9754a5b8
    • M
      x86: fix section mismatch warning - uv_cpu_init · c4bd1fda
      Marcin Slusarz 提交于
      WARNING: vmlinux.o(.cpuinit.text+0x3cc4): Section mismatch in reference from the function uv_cpu_init() to the function .init.text:uv_system_init()
      The function __cpuinit uv_cpu_init() references
      a function __init uv_system_init().
      If uv_system_init is only used by uv_cpu_init then
      annotate uv_system_init with a matching annotation.
      
      uv_system_init was ment to be called only once, so do it from codepath
      (native_smp_prepare_cpus) which is called once, right before activation
      of other cpus (smp_init).
      
      Note: old code relied on uv_node_to_blade being initialized to 0,
      but it'a not initialized from anywhere.
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Acked-by: NJack Steiner <steiner@sgi.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c4bd1fda
    • A
      x86: fix VMI for early params · 3a6ddd5f
      Alok Kataria 提交于
      while fixing a different bug i moved the call to vmi_init before
      early params could be parsed.
      
      This broke the vmi specific commandline parameters.
      Fix that, by moving vmi initialization after kernel has got a chance to
      parse early parameters.
      Signed-off-by: NAlok N Kataria <akataria@vmware.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3a6ddd5f
    • J
      x86: fix two modpost warnings in mm/init_64.c · 9482ac6e
      Jan Beulich 提交于
      early_io{re,un}map() are __init and hence can't be called from __meminit
      functions.
      Signed-off-by: NJan Beulich <jbeulich@novell.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      9482ac6e
    • J
      x86: fix 1:1 mapping init on 64-bit (memory hotplug case) · 8ae3a5a8
      Jan Beulich 提交于
      While I don't have a hotplug capable system at hand, I think two issues need
      fixing:
      
      - pud_phys (in kernel_physical_ampping_init()) would remain uninitialized in
        the after_bootmem case
      
      - the locking done just around phys_pmd_{init,update}() would leave out pgd
        updates, and it was needlessly covering code portions that do allocations
        (perhaps using a more friendly gfp value in alloc_low_page() would then be
        possible)
      Signed-off-by: NJan Beulich <jbeulich@novell.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      8ae3a5a8
    • Y
      x86: work around MTRR mask setting · 38cc1c3d
      Yinghai Lu 提交于
      Joshua Hoblitt reported that only 3 GB of his 16 GB of RAM is
      usable. Booting with mtrr_show showed us the BIOS-initialized
      MTRR settings - which are all wrong.
      
      So the root cause is that the BIOS has not set the mask correctly:
      
      >               [    0.429971]  MSR00000200: 00000000d0000000
      >               [    0.433305]  MSR00000201: 0000000ff0000800
      > should be ==> [    0.433305]  MSR00000201: 0000003ff0000800
      >
      >               [    0.436638]  MSR00000202: 00000000e0000000
      >               [    0.439971]  MSR00000203: 0000000fe0000800
      > should be ==> [    0.439971]  MSR00000203: 0000003fe0000800
      >
      >               [    0.443304]  MSR00000204: 0000000000000006
      >               [    0.446637]  MSR00000205: 0000000c00000800
      > should be ==> [    0.446637]  MSR00000205: 0000003c00000800
      >
      >               [    0.449970]  MSR00000206: 0000000400000006
      >               [    0.453303]  MSR00000207: 0000000fe0000800
      > should be ==> [    0.453303]  MSR00000207: 0000003fe0000800
      >
      >               [    0.456636]  MSR00000208: 0000000420000006
      >               [    0.459970]  MSR00000209: 0000000ff0000800
      > should be ==> [    0.459970]  MSR00000209: 0000003ff0000800
      
      So detect this borkage and add the prefix 111.
      Signed-off-by: NYinghai Lu <yhlu.kernel@gmail.com>
      Cc: <stable@kernel.org>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      38cc1c3d
  4. 21 8月, 2008 9 次提交
  5. 20 8月, 2008 4 次提交
    • A
      x86: fix oprofile + hibernation badness · 80a8c9ff
      Andi Kleen 提交于
      Vegard Nossum reported oprofile + hibernation problems:
      
      > Now some warnings:
      >
      > ------------[ cut here ]------------
      > WARNING: at /uio/arkimedes/s29/vegardno/git-working/linux-2.6/kernel/smp.c:328 s
      > mp_call_function_mask+0x194/0x1a0()
      
      The usual problem: the suspend function when interrupts are
      already disabled calls smp_call_function which is not allowed with
      interrupt off. But at this point all the other CPUs should be already
      down anyways, so it should be enough to just drop that.
      
      This patch should fix that problem at least by fixing cpu hotplug&
      suspend support.
      
      [ mingo@elte.hu: fixed 5 coding style errors. ]
      Signed-off-by: NAndi Kleen <ak@linux.intel.com>
      Tested-by: NVegard Nossum <vegard.nossum@gmail.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      80a8c9ff
    • C
      x86, SGI UV: hardcode the TLB flush interrupt system vector · 99dd8713
      Cliff Wickman 提交于
      The UV TLB shootdown mechanism needs a system interrupt vector.
      
      Its vector had been hardcoded as 200, but needs to moved to the reserved
      system vector range so that it does not collide with some device vector.
      
      This is still temporary until dynamic system IRQ allocation is provided.
      But it will be needed when real UV hardware becomes available and runs 2.6.27.
      Signed-off-by: NCliff Wickman <cpw@sgi.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      99dd8713
    • V
      x86: fix Xorg startup/shutdown slowdown with PAT · 80c5e73d
      Venki Pallipadi 提交于
      Rene Herman reported significant Xorg startup/shutdown slowdown due
      to PAT. It turns out that the memtype list has thousands of entries.
      
      Add cached_entry to list add routine, in order to speed up the
      lookup for sequential reserve_memtype calls.
      Reported-by: NRene Herman <rene.herman@keyaccess.nl>
      Signed-off-by: NVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      80c5e73d
    • S
      x86: fix "kernel won't boot on a Cyrix MediaGXm (Geode)" · c6744955
      Samuel Sieb 提交于
      Cyrix MediaGXm/Cx5530 Unicorn Revision 1.19.3B has stopped
      booting starting at v2.6.22.
      
      The reason is this commit:
      
      > commit f25f64ed
      > Author: Juergen Beisert <juergen@kreuzholzen.de>
      > Date:   Sun Jul 22 11:12:38 2007 +0200
      >
      >     x86: Replace NSC/Cyrix specific chipset access macros by inlined functions.
      
      this commit activated a macro which was dormant before due to (buggy)
      macro side-effects.
      
      I've looked through various datasheets and found that the GXm and GXLV
      Geode processors don't have an incrementor.
      
      Remove the incrementor setup entirely.  As the incrementor value
      differs according to clock speed and we would hope that the BIOS
      configures it correctly, it is probably the right solution.
      
      Cc: <stable@kernel.org>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c6744955
  6. 19 8月, 2008 5 次提交
  7. 18 8月, 2008 11 次提交
    • D
      lockdep: fix spurious 'inconsistent lock state' warning · 6951b12a
      Dmitry Baryshkov 提交于
      Since f82b217e lockdep can output spurious
      warnings related to hwirqs due to hardirq_off shrinkage from int to bit-sized
      flag. Guard it with double negation to fix the warning.
      Signed-off-by: NDmitry Baryshkov <dbaryshkov@gmail.com>
      Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      6951b12a
    • A
      x86: fix build warnings in real mode code · 1b72691c
      Andi Kleen 提交于
      This recent patch
      
      commit c3965bd1
      Author: Paul Jackson <pj@sgi.com>
      Date:   Wed May 14 08:15:34 2008 -0700
      
          x86 boot: proper use of ARRAY_SIZE instead of repeated E820MAX constant
      
      caused these new warnings during a normal build:
      
      In file included from linux-2.6/arch/x86/boot/memory.c:17:
      linux-2.6/include/linux/log2.h: In function '__ilog2_u32':
      linux-2.6/include/linux/log2.h:34: warning: implicit declaration of function 'fls'
      linux-2.6/include/linux/log2.h: In function '__ilog2_u64':
      linux-2.6/include/linux/log2.h:42: warning: implicit declaration of function 'fls64'
      linux-2.6/include/linux/log2.h: In function '__roundup_pow_of_two ':
      linux-2.6/include/linux/log2.h:63: warning: implicit declaration of function 'fls_long'
      
      I tried to fix them in log2.h, but it's difficult because the real mode
      environment is completely different from a normal kernel environment. Instead
      define an own ARRAY_SIZE macro in boot.h, similar to the other private
      macros there.
      Signed-off-by: NAndi Kleen <ak@linux.intel.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      1b72691c
    • M
      x86, calgary: fix section mismatch warning - get_tce_space_from_tar · f7106662
      Marcin Slusarz 提交于
      WARNING: vmlinux.o(.text+0x27032): Section mismatch in reference from the function get_tce_space_from_tar() to the function .init.text:calgary_bus_has_devices()
      The function get_tce_space_from_tar() references
      the function __init calgary_bus_has_devices().
      This is often because get_tce_space_from_tar lacks a __init
      annotation or the annotation of calgary_bus_has_devices is wrong.
      
      get_tce_space_from_tar is called only from __init function (calgary_init)
      and calls __init function (calgary_bus_has_devices).
      So annotate it properly.
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Cc: Chandru Siddalingappa <chandru@in.ibm.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      f7106662
    • M
      x86: silence section mismatch warning - get_local_pda · d19fbfdf
      Marcin Slusarz 提交于
      Take out part of get_local_pda referencing __init function (free_bootmem)
      to new (static) function marked as __ref. It's safe to do because free_bootmem
      is called before __init sections are dropped.
      
      WARNING: vmlinux.o(.cpuinit.text+0x3cd7): Section mismatch in reference from the function get_local_pda() to the function .init.text:free_bootmem()
      The function __cpuinit get_local_pda() references
      a function __init free_bootmem().
      If free_bootmem is only used by get_local_pda then
      annotate free_bootmem with a matching annotation.
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Cc: Mike Travis <travis@sgi.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      d19fbfdf
    • M
      x86, percpu: silence section mismatch warnings related to EARLY_PER_CPU variables · c6a92a25
      Marcin Slusarz 提交于
      Quoting Mike Travis in "x86: cleanup early per cpu variables/accesses v4"
      (23ca4bba):
      
          The DEFINE macro defines the per_cpu variable as well as the early
          map and pointer.  It also initializes the per_cpu variable and map
          elements to "_initvalue".  The early_* macros provide access to
          the initial map (usually setup during system init) and the early
          pointer.  This pointer is initialized to point to the early map
          but is then NULL'ed when the actual per_cpu areas are setup.  After
          that the per_cpu variable is the correct access to the variable.
      
      As these variables are NULL'ed before __init sections are dropped
      (in setup_per_cpu_maps), they can be safely annotated as __ref.
      
      This change silences following section mismatch warnings:
      
      WARNING: vmlinux.o(.data+0x46c0): Section mismatch in reference from the variable x86_cpu_to_apicid_early_ptr to the variable .init.data:x86_cpu_to_apicid_early_map
      The variable x86_cpu_to_apicid_early_ptr references
      the variable __initdata x86_cpu_to_apicid_early_map
      If the reference is valid then annotate the
      variable with __init* (see linux/init.h) or name the variable:
      *driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,
      
      WARNING: vmlinux.o(.data+0x46c8): Section mismatch in reference from the variable x86_bios_cpu_apicid_early_ptr to the variable .init.data:x86_bios_cpu_apicid_early_map
      The variable x86_bios_cpu_apicid_early_ptr references
      the variable __initdata x86_bios_cpu_apicid_early_map
      If the reference is valid then annotate the
      variable with __init* (see linux/init.h) or name the variable:
      *driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,
      
      WARNING: vmlinux.o(.data+0x46d0): Section mismatch in reference from the variable x86_cpu_to_node_map_early_ptr to the variable .init.data:x86_cpu_to_node_map_early_map
      The variable x86_cpu_to_node_map_early_ptr references
      the variable __initdata x86_cpu_to_node_map_early_map
      If the reference is valid then annotate the
      variable with __init* (see linux/init.h) or name the variable:
      *driver, *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console,
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Cc: Mike Travis <travis@sgi.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c6a92a25
    • D
      x86: fix i486 suspend to disk CR4 oops · e532c06f
      David Fries 提交于
      arch/x86/power/cpu_32.c __save_processor_state calls read_cr4()
      only a i486 CPU doesn't have the CR4 register.  Trying to read it
      produces an invalid opcode oops during suspend to disk.
      
      Use the safe rc4 reading op instead. If the value to be written is
      zero the write is skipped.
      
      arch/x86/power/hibernate_asm_32.S
      done: swapped the use of %eax and %ecx to use jecxz for
      the zero test and jump over store to %cr4.
      restore_image: s/%ecx/%eax/ to be consistent with done:
      
      In addition to __save_processor_state, acpi_save_state_mem,
      efi_call_phys_prelog, and efi_call_phys_epilog had checks added
      (acpi restore was in assembly and already had a check for
      non-zero).  There were other reads and writes of CR4, but MCE and
      virtualization shouldn't be executed on a i486 anyway.
      Signed-off-by: NDavid Fries <david@fries.net>
      Acked-by: NH. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      e532c06f
    • M
      x86: mpparse.c: fix section mismatch warning · 39e00fe2
      Marcin Slusarz 提交于
      WARNING: vmlinux.o(.text+0x118f7): Section mismatch in reference from the function construct_ioapic_table() to the function .init.text:MP_bus_info()
      The function construct_ioapic_table() references
      the function __init MP_bus_info().
      This is often because construct_ioapic_table lacks a __init
      annotation or the annotation of MP_bus_info is wrong.
      
      construct_ioapic_table is called only from construct_default_ISA_mptable which is __init
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      39e00fe2
    • M
      x86: mmconf: fix section mismatch warning · c72a5efe
      Marcin Slusarz 提交于
      WARNING: arch/x86/kernel/built-in.o(.cpuinit.text+0x1591): Section mismatch in reference from the function init_amd() to the function .init.text:check_enable_amd_mmconf_dmi()
      The function __cpuinit init_amd() references
      a function __init check_enable_amd_mmconf_dmi().
      If check_enable_amd_mmconf_dmi is only used by init_amd then
      annotate check_enable_amd_mmconf_dmi with a matching annotation.
      
      check_enable_amd_mmconf_dmi is only called from init_amd which is __cpuinit
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c72a5efe
    • M
      x86: fix MP_processor_info section mismatch warning · 67d0c9eb
      Marcin Slusarz 提交于
      WARNING: arch/x86/kernel/built-in.o(.cpuinit.text+0x1fe7): Section mismatch in reference from the function MP_processor_info() to the variable .init.data:x86_quirks
      The function __cpuinit MP_processor_info() references
      a variable __initdata x86_quirks.
      If x86_quirks is only used by MP_processor_info then
      annotate x86_quirks with a matching annotation.
      
      MP_processor_info uses x86_quirks which is __init and is used only from
      smp_read_mpc and construct_default_ISA_mptable which are __init
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      67d0c9eb
    • M
      x86, tsc: fix section mismatch warning · d554d9a4
      Marcin Slusarz 提交于
      WARNING: vmlinux.o(.text+0x7950): Section mismatch in reference from the function native_calibrate_tsc() to the function .init.text:tsc_read_refs()
      The function native_calibrate_tsc() references
      the function __init tsc_read_refs().
      This is often because native_calibrate_tsc lacks a __init
      annotation or the annotation of tsc_read_refs is wrong.
      
      tsc_read_refs is called from native_calibrate_tsc which is not __init
      and native_calibrate_tsc cannot be marked __init
      Signed-off-by: NMarcin Slusarz <marcin.slusarz@gmail.com>
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      d554d9a4
    • M
      x86: correct register constraints for 64-bit atomic operations · 3c3b5c3b
      Mathieu Desnoyers 提交于
      x86_64 add/sub atomic ops does not seems to accept integer values bigger
      than 32 bits as immediates. Intel's add/sub documentation specifies they
      have to be passed as registers.
      
      The only operations in the x86-64 architecture which accept arbitrary
      64-bit immediates is "movq" to any register; similarly, the only
      operation which accept arbitrary 64-bit displacement is "movabs" to or
      from al/ax/eax/rax.
      
      http://gcc.gnu.org/onlinedocs/gcc-4.3.0/gcc/Machine-Constraints.html
      
      states :
      
      e
          32-bit signed integer constant, or a symbolic reference known to fit
          that range (for immediate operands in sign-extending x86-64
          instructions).
      Z
          32-bit unsigned integer constant, or a symbolic reference known to
          fit that range (for immediate operands in zero-extending x86-64
          instructions).
      
      Since add/sub does sign extension, using the "e" constraint seems appropriate.
      
      It applies to 2.6.27-rc, 2.6.26, 2.6.25...
      Signed-off-by: NMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
      Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      Signed-off-by: NIngo Molnar <mingo@elte.hu>
      3c3b5c3b