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    SubjectRe: PCIE
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    From: Grant Grundler <grundler@parisc-linux.org>
    Date: Sat, 26 May 2007 18:16:31 -0600

    > Are they really? The device is generating the transaction on the bus.
    > The PCI host controller (in general) will be routing that transaction
    > to wherever the "dest addr" of the MSI lives. It doesn't have to be
    > in the CPU but it will certainly be a proxy for that CPU if it's not.
    > We won't care if the proxy only have one IRQ line going to the CPU
    > as long as the de-muxing of the "data" portion results in a unique
    > identifier that can be mapped to exactly one interrupt handler.

    True, on sparc64 PCI-E controllers, for example, the MSI vector is
    received by the PCI-E host controller, and the host controller turns
    this into a cpu format interrupt packet for the system bus.

    I guess on IRQ pin starved systems, the PCI-E host controller or
    something similar would get interrogated by the cpu for the MSI vector
    number.

    I don't want to be the person who has to code up support for
    that, as it's not easy to shim mid-level vectoring into the
    generic IRQ layer currently. I'd love to be able to do that
    on sparc64 instead of what arch/sparc64/kernel/pci_sun4v.c's
    pci_sun4v_msi_prehandler() is doing.

    There is a lot of information and vectoring capabilities present
    that I'm simply not taking advantage of yet :-)
    -
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