Re: [PATCH v6 0/2] kvm: level irqfd and new eoifd

From: Alex Williamson
Date: Mon Jul 23 2012 - 18:51:42 EST

On Fri, 2012-07-20 at 10:33 -0600, Alex Williamson wrote:
> v6:
> So we're back to just the first two patches, unfortunately the
> diffstat got bigger though. The reason for that is that I discovered
> we don't do anything on release of an eoifd. We cleanup if the kvm
> vm is released, but we're dealing with a constrained resource of irq
> source IDs, so I think it's best that we cleanup to make sure those
> are returned. To do that we need nearly the same infrastructure as
> irqfd, we just only watch for POLLHUP. So while there's more code
> here, the structure and function names line up identically to irqfd.
> The other big change here is that KVM_IRQFD returns a token when
> setting up a level irqfd. We use this token to associate the eoifd
> with the right source. This means we have to put the struct
> _source_ids on a list so we can find them. This removes the weird
> interaction we were headed to where the eoifd is associated with
> the eventfd of the irqfd. There's potentially more flexibility for
> the future here too as we might come up with other interfaces that
> can return a source ID "key". Perhaps some future KVM_IRQFD will
> allow specifying a key for re-attaching. Anyway, the sequence
> Michael pointed out where an irqfd is de-assigned then re-assigned
> now results in a new key instead of leaving the user wondering if
> it re-associates back to the eoifd.
> Also added workqueue flushes on assign since releasing either
> object now results in a lazy release via workqueue. This ensures
> we re-claim any source IDs we can. Thanks,

FYI, I seem to have found a new locking issue in this version. I'll
send an update when I find it. Thanks,


> ---
> Alex Williamson (2):
> kvm: KVM_EOIFD, an eventfd for EOIs
> kvm: Extend irqfd to support level interrupts
> Documentation/virtual/kvm/api.txt | 32 ++-
> arch/x86/kvm/x86.c | 3
> include/linux/kvm.h | 18 +
> include/linux/kvm_host.h | 17 +
> virt/kvm/eventfd.c | 463 ++++++++++++++++++++++++++++++++++++-
> virt/kvm/kvm_main.c | 11 +
> 6 files changed, 536 insertions(+), 8 deletions(-)

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