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    SubjectRe: [PATCH v5 0/4] kvm: level irqfd and new eoifd
    On Mon, Jul 16, 2012 at 02:33:38PM -0600, Alex Williamson wrote:
    > v5:
    > - irqfds now have a one-to-one mapping with eoifds to prevent users
    > from consuming all of kernel memory by repeatedly creating eoifds
    > from a single irqfd.
    > - implement a kvm_clear_irq() which does a test_and_clear_bit of
    > the irq_state, only updating the pic/ioapic if changes and allowing
    > the caller to know if anything was done. I added this onto the end
    > as it's essentially an optimization on the previous design. It's
    > hard to tell if there's an actual performance benefit to this.
    > - dropped eoifd gsi support patch as it was only an FYI.
    >
    > Thanks,
    >
    > Alex


    So 3/4, 4/4 are racy and I think you convinced me it's best to drop it for
    now. I hope that fact that we already scan all vcpus under spinlock for
    level interrupts is enough to justify adding a lock here.

    To summarize issues still outstanding with 1/2, 2/2:
    - source id lingering after irqfd was destroyed/deassigned
    prevents assigning a new irqfd
    - if same irqfd is deassigned and re-assigned, this
    seems to succeed but does not give any more EOIs
    - document that user needs to re-inject interrupts
    injected by level IRQFD after migration as they are cleared

    Hope this helps!

    > ---
    >
    > Alex Williamson (4):
    > kvm: Convert eoifd to use kvm_clear_irq
    > kvm: Create kvm_clear_irq()
    > kvm: KVM_EOIFD, an eventfd for EOIs
    > kvm: Extend irqfd to support level interrupts
    >
    >
    > Documentation/virtual/kvm/api.txt | 28 +++
    > arch/x86/kvm/x86.c | 3
    > include/linux/kvm.h | 18 ++
    > include/linux/kvm_host.h | 16 ++
    > virt/kvm/eventfd.c | 333 +++++++++++++++++++++++++++++++++++++
    > virt/kvm/irq_comm.c | 78 +++++++++
    > virt/kvm/kvm_main.c | 11 +
    > 7 files changed, 483 insertions(+), 4 deletions(-)


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