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SubjectRe: booting "nosmp" kernel causing ACPI errors
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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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