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    SubjectRe: [PATCH -v2 5/5] x86: use dmi check to treat disabled cpus as hotplug cpus.
    On 01/12/2010 06:06 PM, Suresh Siddha wrote:
    > On Tue, 2010-01-12 at 17:55 -0800, Yinghai Lu wrote:
    >> you mean this blacklist could be too long?
    >
    > yes.
    >
    >>
    >> switch to whitelist for the box can treat disabled cpus as hotplug
    >> cpus?
    >
    > Do we really need all this? Systems which support physical hotplug
    > typically have lot's of cpu's (mostly will have atleast > 8). Even if we
    > really need to identify, then perhaps we can check if ACPI has any hints
    > regarding the physical hotplug support at boot time (we should check
    > with Andi Kleen or Len Brown on this).
    >
    > For now, I think we can keep it simple by using the detected enabled
    > cpu's.

    sth like this ?

    ---
    arch/x86/kernel/smpboot.c | 3 +--
    1 file changed, 1 insertion(+), 2 deletions(-)

    Index: linux-2.6/arch/x86/kernel/smpboot.c
    ===================================================================
    --- linux-2.6.orig/arch/x86/kernel/smpboot.c
    +++ linux-2.6/arch/x86/kernel/smpboot.c
    @@ -1190,7 +1190,6 @@ early_param("possible_cpus", _setup_poss
    * - Ashok Raj
    *
    * Three ways to find out the number of additional hotplug CPUs:
    - * - If the BIOS specified disabled CPUs in ACPI/mptables use that.
    * - The user can overwrite it with possible_cpus=NUM
    * - Otherwise don't reserve additional CPUs.
    * We do this because additional CPUs waste a lot of memory.
    @@ -1205,7 +1204,7 @@ __init void prefill_possible_map(void)
    num_processors = 1;

    if (setup_possible_cpus == -1)
    - possible = num_processors + disabled_cpus;
    + possible = num_processors;
    else
    possible = setup_possible_cpus;


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