Messages in this thread | | | Date | Fri, 11 Nov 2011 13:24:08 -0500 | From | Konrad Rzeszutek Wilk <> | Subject | Re: [PATCH v3 5/7] Documentations/cpu-hotplug.tx, kernel-parameters.txt: Add x86 CPU0 online/offline feature |
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On Wed, Nov 09, 2011 at 04:34:15PM -0800, Fenghua Yu wrote: > From: Fenghua Yu <fenghua.yu@intel.com> > > Add x86 CPU0 online/offline feature in the two documentations. > > By default BSP is not pluggable. Kernel parameter bsp_hotplug enables BSP > online/offline feature. > > The documentations point out two BSP dependencies. First, resume from hibernate > or suspend always starts from BSP. So hibernate and suspend are prevented if BSP > is offline. Another dependency is PIC interrupts always go to BSP. > > It's said that some machines may depend on CPU0 to poweroff/reboot. But I > haven't seen such dependency on a few tested machines. > > Please let me know if you see any CPU0 dependencies on your machine. > > Signed-off-by: Fenghua Yu <fenghua.yu@intel.com> > --- > --- > Documentation/cpu-hotplug.txt | 19 +++++++++++++++++++ > Documentation/kernel-parameters.txt | 13 +++++++++++++ > 2 files changed, 32 insertions(+), 0 deletions(-) > > diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt > index a20bfd4..93af1a0 100644 > --- a/Documentation/cpu-hotplug.txt > +++ b/Documentation/cpu-hotplug.txt > @@ -207,6 +207,25 @@ by making it not-removable. > > In such cases you will also notice that the online file is missing under cpu0. > > +Q: Is CPU0 removable on X86? > +A: Yes. If given kernel option bsp_hotplug, CPU0 is removable. > + > +But some features depend on BSP. Known dependencies are: > +1. Resume from hibernate/suspend depends on BSP. Hibernate/suspend will fail if > +BSP is offline and you need to online BSP before hibernate/suspend can continue. > +2. PIC interrupts also depend on BSP. BSP can't be removed if a PIC interrupt > +is detected. > + > +It's said poweroff/reboot may depend on BSP on some machines although I haven't > +seen any poweroff/reboot failure so far after BSP is offline on a few tested > +machines. > + > +Please let me know if you know or see any other dependencies of BSP.
You should include your email so folks can contact you.
> + > +If the dependencies are under your control, you can turn on bsp_hotplug. > + > +--Fenghua Yu > + > Q: How do i find out if a particular CPU is not removable? > A: Depending on the implementation, some architectures may show this by the > absence of the "online" file. This is done if it can be determined ahead of > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index a0c5c5f..55582db 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -1842,6 +1842,19 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > > nox2apic [X86-64,APIC] Do not enable x2APIC mode. > > + bsp_hotplug [X86] BSP (aka CPU0) is hotpluggable. > + Some features depend on BSP. Known dependencies are: > + 1. Resume from suspend/hibernate depends on BSP. > + Suspend/hibernate will fail if BSP is offline and you > + need to online BSP before suspend/hibernate. > + 2. PIC interrupts also depend on BSP. BSP can't be > + removed if a PIC interrupt is detected. > + It's said poweroff/reboot may depend on BSP on some > + machines although I haven't seen such issues so far > + after BSP is offline on a few tested machines. > + If the dependencies are under your control, you can > + turn on bsp_hotplug. > + > nptcg= [IA-64] Override max number of concurrent global TLB > purges which is reported from either PAL_VM_SUMMARY or > SAL PALO. > -- > 1.6.0.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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