Re: [beta patch] SSE copy_page() / clear_page()

From: Manfred Spraul (manfred@colorfullife.com)
Date: Sat Feb 10 2001 - 13:18:00 EST

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    Manfred Spraul wrote:
    >
    > copy_*_user is probably not worth the effort for a Pentium III, but even
    > for that function I don't see a problem with SSE, as long as
    >
    > * the clobbered registers are stored on the stack (and not in
    > thread.i387.fxsave)
    > * the SSE/SSE2 instructions can't cause SIMD exceptions.
    > * noone saves the fpu state into thread.i387.fxsave from interrupts /
    > softirq's. Currently it's impossible, but I haven't checked Montavista's
    > preemptive kernel scheduler.
    >
    I overlooked one restriction:
    * you must not schedule() with the "wrong" sse registers: switch_to()
    saves into i387.fxsave.

    This means that copy_*_user isn't that simple. 

    --
	Manfred
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