Seeking clarification to the original question I posted: >> >> > This maybe a novice question - Would appreciate it if you can you provide a > pointer to documentation or relevant code that explains what is the > *limitation in supporting level irq support in kvm irqfd.* > > > After browsing the KVM kernel code, it does look like direct assignment of PCI devices allows support for level-triggered interrupts to be injected to the guest from the kernel. (*as opposed to not supporting it for vhost irqfd mechanism*) This occurs when the guest device supports INTX. Reference: kvm_assigned_dev_interrupt_work_handler() in assigned-dev.c calls kvm_set_irq() with the guest_irq. This function in turn invokes the assigned set function (either kvm_set_pic_irq or kvm_set_ioapic_irq) which was setup at kvm_irq_chip creation time when kvm_setup_default_irq_routing () called for handling ioctl KVM_CREATE_IRQCHIP.
So, it isn't clear why level-triggered interrupt isn't supported for irqfd mechanism. Would greatly appreciate clarification here Thanks -Rukhsana
