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    SubjectRe: [BUG] perf: bogus correlation of kernel symbols
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    On Fri, 2011-05-20 at 15:11 +0200, Ingo Molnar wrote:

    > We need to allocate the IDT dynamically: just kmalloc() it, update idt_descr
    > and do a load_idt(). Double check places that modify idt_descr or use
    > idt_table.
    >
    > Note, you could do this as a side effect of a nice performance optimization:
    > would you be interested in allocating it in the percpu area, using
    > percpu_alloc()? That way the IDT is distributed between CPUs - this has
    > scalability advantages on NUMA systems and maybe even on SMP.
    >

    Any suggestions on when this allocation should take place? I'm hesitant
    to touch anything in arch/x86/kernel/head_32.S, where the IDT is setup
    and lidt idt_descr is called (on x86-32 anyway). That means at some
    point I'd have to copy the table into a region allocated with
    alloc_percpu() and set up a new descriptor. Seems like this should
    happen before IRQ is enabled, but I'm not sure about the best place.

    Also, I'd still welcome suggestions on generating entropy so early in
    the boot process as to randomize the location at which the kernel is
    decompressed.

    On a related note, would there be obstacles to marking the IDT as
    read-only?

    Thanks,
    Dan



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