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    SubjectRe: Multiple MSI, take 3
    On Fri, Jul 11, 2008 at 03:59:59PM -0700, Eric W. Biederman wrote:
    > Suresh Siddha <suresh.b.siddha@intel.com> writes:
    >
    > > With interrupt-remapping, we can program the individual interrupt
    > > remapping table entries to point to different cpu's etc. All we have
    > > to take care is, do the IRTE allocation in a consecutive block and
    > > program the starting index to the MSI registers.
    > >
    > > Just curious Eric, why do you think that won't work?
    >
    > Working mask/unmask. With MSI-X as specced if I mask an irq and then unmask
    > it, an msi message will fire if something happened while the irq was masked
    > and not taken care of before the irq was unmasked. That is the correct
    > behavior for an irq and a mmu won't let me get that.

    And why do we need to mask/unmask the device in the interrupt-remapping case?

    >
    > The best I can do with an iommu is to run delayed disable and set the
    > interrupt remapping slot in the iommu to reject the traffic. Which
    > is almost but not quite what I want.
    >
    > Overall introducing a new concept into the linux irq model seems a lot
    > cleaner and more portable, and even there we are likely to be a lot
    > more fragile because of the difficulty in obtaining contiguous
    > vectors.
    >
    > Speaking of. How many interrupt targets does the dmar iommu have
    > for interrupts? 16K?

    There can be multiple interrupt-remapping units in the platform and
    each of table in the remapping unit has max 64K entries.

    thanks,
    suresh


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