Re: [PATCH v5 0/4] kvm: level irqfd and new eoifd
From: Michael S. Tsirkin
Date: Thu Jul 19 2012 - 12:59:27 EST
On Mon, Jul 16, 2012 at 02:33:38PM -0600, Alex Williamson wrote:
> - 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.
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(-)
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/