Re: [PATCH 0/5] Threaded MSI interrupt for VFIO PCI device

Paolo Bonzini
2015-12-16T17:56:52Z

Alex,

can you take a look at the extension to the irq bypass interface in
patch 2? I'm not sure I understand what is the case where you have
multiple consumers for the same token.

Paolo

On 03/12/2015 19:22, Yunhong Jiang wrote:
> When assigning a VFIO device to a KVM guest with low latency requirement, it
> is better to handle the interrupt in the hard interrupt context, to reduce
> the context switch to/from the IRQ thread.
>
> Based on discussion on https://lkml.org/lkml/2015/10/26/764, the VFIO msi
> interrupt is changed to use request_threaded_irq(). The primary interrupt
> handler tries to set the guest interrupt atomically. If it fails to achieve
> it, a threaded interrupt handler will be invoked.
>
> The irq_bypass manager is extended for this purpose. The KVM eventfd will
> provide a irqbypass consumer to handle the interrupt at hard interrupt
> context. The producer will invoke the consumer's handler then.
>
> Yunhong Jiang (5):
> Extract the irqfd_wakeup_pollin/irqfd_wakeup_pollup
> Support runtime irq_bypass consumer
> Support threaded interrupt handling on VFIO
> Add the irq handling consumer
> Expose x86 kvm_arch_set_irq_inatomic()
>
> arch/x86/kvm/Kconfig | 1 +
> drivers/vfio/pci/vfio_pci_intrs.c | 39 ++++++++++--
> include/linux/irqbypass.h | 8 +++
> include/linux/kvm_host.h | 19 +++++-
> include/linux/kvm_irqfd.h | 1 +
> virt/kvm/Kconfig | 3 +
> virt/kvm/eventfd.c | 131 ++++++++++++++++++++++++++------------
> virt/lib/irqbypass.c | 82 ++++++++++++++++++------
> 8 files changed, 214 insertions(+), 70 deletions(-)
>