> > The existing KVM mechanism for forwarding of level-triggered interrupts using > resample eventfd doesn't work quite correctly in the case of interrupts that are > handled in a Linux guest as oneshot interrupts (IRQF_ONESHOT). Such an > interrupt is acked to the device in its threaded irq handler, i.e. later than it is > acked to the interrupt controller (EOI at the end of hardirq), not earlier. The > existing KVM code doesn't take that into account, which results in erroneous > extra interrupts in the guest caused by premature re-assert of an > unacknowledged IRQ by the host. Interesting... How it behaviors in native side? > > This patch series fixes this issue (for now on x86 only) by checking if the > interrupt is unmasked when we receive irq ack (EOI) and, in case if it's masked, > postponing resamplefd notify until the guest unmasks it. > > Patches 1 and 2 extend the existing support for irq mask notifiers in KVM, > which is a prerequisite needed for KVM irqfd to use mask notifiers to know > when an interrupt is masked or unmasked. > > Patch 3 implements the actual fix: postponing resamplefd notify in irqfd until > the irq is unmasked. > > Patches 4 and 5 just do some optional renaming for consistency, as we are now > using irq mask notifiers in irqfd along with irq ack notifiers. > > Please see individual patches for more details. > > v2: > - Fixed compilation failure on non-x86: mask_notifier_list moved from > x86 "struct kvm_arch" to generic "struct kvm". > - kvm_fire_mask_notifiers() also moved from x86 to generic code, even > though it is not called on other architectures for now. > - Instead of kvm_irq_is_masked() implemented > kvm_register_and_fire_irq_mask_notifier() to fix potential race > when reading the initial IRQ mask state. > - Renamed for clarity: > - irqfd_resampler_mask() -> irqfd_resampler_mask_notify() > - kvm_irq_has_notifier() -> kvm_irq_has_ack_notifier() > - resampler->notifier -> resampler->ack_notifier > - Reorganized code in irqfd_resampler_ack() and > irqfd_resampler_mask_notify() to make it easier to follow. > - Don't follow unwanted "return type on separate line" style for > irqfd_resampler_mask_notify(). > > Dmytro Maluka (5): > KVM: x86: Move irq mask notifiers from x86 to generic KVM > KVM: x86: Add kvm_register_and_fire_irq_mask_notifier() > KVM: irqfd: Postpone resamplefd notify for oneshot interrupts > KVM: irqfd: Rename resampler->notifier > KVM: Rename kvm_irq_has_notifier() > > arch/x86/include/asm/kvm_host.h | 17 +--- > arch/x86/kvm/i8259.c | 6 ++ > arch/x86/kvm/ioapic.c | 8 +- > arch/x86/kvm/ioapic.h | 1 + > arch/x86/kvm/irq_comm.c | 74 +++++++++++------ > arch/x86/kvm/x86.c | 1 - > include/linux/kvm_host.h | 21 ++++- > include/linux/kvm_irqfd.h | 16 +++- > virt/kvm/eventfd.c | 136 ++++++++++++++++++++++++++++---- > virt/kvm/kvm_main.c | 1 + > 10 files changed, 221 insertions(+), 60 deletions(-) > > -- > 2.37.1.559.g78731f0fdb-goog
