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    SubjectRe: booting "nosmp" kernel causing ACPI errors
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    Date
    Hi, Bernard,

    On Wed, 2010-10-20 at 05:45 +0800, Bernard Pidoux wrote:
    > Hi,
    >
    > I needed to run Linux on UP mode in order to perform some application tests.
    > Using nosmp argument lead to bad interrupts set up.
    >
    do you want to run a up kernel or just want to enable one processor?

    > I finally found the explanation I was looking for in this acpi-linux
    > thread :
    > http://marc.info/?l=linux-acpi&m=118794015205199&w=4
    >
    > maxcpus= [SMP] Maximum number of processors that an SMP kernel
    > should make use of. maxcpus=n : n>= 0 limits the
    > kernel to using 'n' processors. n=0 is a special case,
    > it is equivalent to "nosmp", which also disables
    > the IO APIC.
    >
    > nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
    > and disable the IO APIC. legacy for "maxcpus=0".
    >
    >
    > I understand that the reason why nosmp also disable IO APIC is for
    > backward compatibility.
    > However this is not intuitive : one argument leading to two actions.
    >
    > So, if I want to run my dual core CPU in UniProcessor mode I have to use
    > kernel argument maxcpus=1 in grub/menu.lst
    >
    that's correct, but note that you're still running a smp kernel in this
    case.

    when using maxcpus=1, you're running a *_smp_* kernel, which detects one
    processor and stops.
    when using maxcpus=0, you're running a up kernel which surely doesn't
    have the ioapic support, and is not able to detect the other processors.

    thanks,
    rui
    > Doing so, interrupts on my Linux system are correctly initialized and it
    > is much more stable.
    >
    > Bernard
    >
    >
    >
    > Le 16/10/2010 18:45, Bernard Pidoux a écrit :
    > > Hi,
    > >
    > > I observed ACPI errors when booting 2.6.35.7 kernel with "nosmp"
    > > argument.
    > > dmesg shows a warning message starting with :
    > > WARNING: at mm/page_alloc.c:1981 __alloc_pages_nodemask+0x5b4/0x6d0()
    > > +Hardware name: MS-7519
    > > +Modules linked in:
    > > +Pid: 1, comm: swapper Not tainted 2.6.35.7 #2
    > >
    > > This is followed by ACPI error messages and /proc/interrupts show that
    > > interrupts 0-15 are then handled by XT-PIC-XT
    > > instead of IO-APIC-edge and IO-APIC-fasteoi when runing smp kernel.
    > >
    > > Here is lspci dump :
    > >
    > > 00:00.0 Host bridge: Intel Corporation 4 Series Chipset DRAM
    > > Controller (rev 03)
    > > 00:01.0 PCI bridge: Intel Corporation 4 Series Chipset PCI Express
    > > Root Port (rev 03)
    > > 00:1a.0 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB
    > > UHCI Controller #4
    > > 00:1a.1 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB
    > > UHCI Controller #5
    > > 00:1a.2 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB
    > > UHCI Controller #6
    > > 00:1a.7 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB2
    > > EHCI Controller #2
    > > 00:1b.0 Audio device: Intel Corporation 82801JI (ICH10 Family) HD
    > > Audio Controller
    > > 00:1c.0 PCI bridge: Intel Corporation 82801JI (ICH10 Family) PCI
    > > Express Root Port 1
    > > 00:1c.1 PCI bridge: Intel Corporation 82801JI (ICH10 Family) PCI
    > > Express Port 2
    > > 00:1c.5 PCI bridge: Intel Corporation 82801JI (ICH10 Family) PCI
    > > Express Root Port 6
    > > 00:1d.0 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB
    > > UHCI Controller #1
    > > 00:1d.1 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB
    > > UHCI Controller #2
    > > 00:1d.2 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB
    > > UHCI Controller #3
    > > 00:1d.7 USB Controller: Intel Corporation 82801JI (ICH10 Family) USB2
    > > EHCI Controller #1
    > > 00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 90)
    > > 00:1f.0 ISA bridge: Intel Corporation 82801JIB (ICH10) LPC Interface
    > > Controller
    > > 00:1f.2 IDE interface: Intel Corporation 82801JI (ICH10 Family) 4 port
    > > SATA IDE Controller #1
    > > 00:1f.3 SMBus: Intel Corporation 82801JI (ICH10 Family) SMBus Controller
    > > 00:1f.5 IDE interface: Intel Corporation 82801JI (ICH10 Family) 2 port
    > > SATA IDE Controller #2
    > > 01:00.0 VGA compatible controller: nVidia Corporation G98 [GeForce
    > > 8400 GS] (rev a1)
    > > 02:00.0 IDE interface: JMicron Technology Corp. JMB368 IDE controller
    > > 04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
    > > RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 02)
    > >
    > > I observed the same issue with another machine with also an MSI
    > > motherboard but using a PCI bridge VIA VT8237/VX700
    > > even when booting with "pci=use_crs" argument.
    > >
    > > Attached is diff -ruN file between 2.6.35.7 kernel without and with
    > > "nosmp" boot argument.
    > >
    > > Bernard
    > >
    >
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