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KVM: Add resampling irqfds for level triggered interrupts

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To emulate level triggered interrupts, add a resample option to
KVM_IRQFD.  When specified, a new resamplefd is provided that notifies
the user when the irqchip has been resampled by the VM.  This may, for
instance, indicate an EOI.  Also in this mode, posting of an interrupt
through an irqfd only asserts the interrupt.  On resampling, the
interrupt is automatically de-asserted prior to user notification.
This enables level triggered interrupts to be posted and re-enabled
from vfio with no userspace intervention.

All resampling irqfds can make use of a single irq source ID, so we
reserve a new one for this interface.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Alex Williamson
2012-09-21 11:58:03 -06:00
committed by Avi Kivity
parent 1e08ec4a13
commit 7a84428af7
6 changed files with 184 additions and 6 deletions
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4
arch/x86/kvm/x86.c
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@@ -2176,6 +2176,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_PCI_2_3:
case KVM_CAP_KVMCLOCK_CTRL:
case KVM_CAP_READONLY_MEM:
case KVM_CAP_IRQFD_RESAMPLE:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
@@ -6268,6 +6269,9 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
set_bit(KVM_USERSPACE_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);
/* Reserve bit 1 of irq_sources_bitmap for irqfd-resampler */
set_bit(KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
&kvm->arch.irq_sources_bitmap);
raw_spin_lock_init(&kvm->arch.tsc_write_lock);
mutex_init(&kvm->arch.apic_map_lock);