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    SubjectRe: [Lguest] [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes
    Avi Kivity wrote:
    >
    >> Here is a prototype patch of the compressed IRQ stubs -- this patch
    >> compresses them down to 7 stubs per 32-byte cache line (or part of cache
    >> line) at the expense of a back-to-back jmp which has the potential of
    >> being ugly on some pipelines (we can only get 4 stubs into 32 bytes
    >> without that).
    >
    > You could actually get 4-byte stubs, using a 16-bit call (66 e8 ww ww).
    > But it would be slower, since we won't be pairing it with a ret.
    >

    Yes, I would consider that a theoretical exercise only :)

    > I suspect we could get it down to three bytes, by sharing the last byte
    > of the four-byte call sequence with the first byte of the next:
    >
    > 66 e8 ff 66 e8 fc 66 e8 f9 66 e8 f6 ...
    >
    > Every three bytes a new stub begins; it's a four-byte call to offset
    > 0x6703 relative to the beginning of the first stub.
    >
    > Can anyone better 24 bits/stub?

    On the entirely silly level...

    CC xx

    -hpa


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