diff options
Diffstat (limited to 'arch/x86/kvm/ioapic.c')
| -rw-r--r-- | arch/x86/kvm/ioapic.c | 37 |
1 files changed, 34 insertions, 3 deletions
diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c index 765943d7cfa5..995eb5054360 100644 --- a/arch/x86/kvm/ioapic.c +++ b/arch/x86/kvm/ioapic.c @@ -26,6 +26,7 @@ * Yaozu (Eddie) Dong <eddie.dong@intel.com> * Based on Xen 3.1 code. */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/kvm_host.h> #include <linux/kvm.h> @@ -367,9 +368,39 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) mask_after = e->fields.mask; if (mask_before != mask_after) kvm_fire_mask_notifiers(ioapic->kvm, KVM_IRQCHIP_IOAPIC, index, mask_after); - if (e->fields.trig_mode == IOAPIC_LEVEL_TRIG - && ioapic->irr & (1 << index)) - ioapic_service(ioapic, index, false); + if (e->fields.trig_mode == IOAPIC_LEVEL_TRIG && + ioapic->irr & (1 << index) && !e->fields.mask && !e->fields.remote_irr) { + /* + * Pending status in irr may be outdated: the IRQ line may have + * already been deasserted by a device while the IRQ was masked. + * This occurs, for instance, if the interrupt is handled in a + * Linux guest as a oneshot interrupt (IRQF_ONESHOT). In this + * case the guest acknowledges the interrupt to the device in + * its threaded irq handler, i.e. after the EOI but before + * unmasking, so at the time of unmasking the IRQ line is + * already down but our pending irr bit is still set. In such + * cases, injecting this pending interrupt to the guest is + * buggy: the guest will receive an extra unwanted interrupt. + * + * So we need to check here if the IRQ is actually still pending. + * As we are generally not able to probe the IRQ line status + * directly, we do it through irqfd resampler. Namely, we clear + * the pending status and notify the resampler that this interrupt + * is done, without actually injecting it into the guest. If the + * IRQ line is actually already deasserted, we are done. If it is + * still asserted, a new interrupt will be shortly triggered + * through irqfd and injected into the guest. + * + * If, however, it's not possible to resample (no irqfd resampler + * registered for this irq), then unconditionally inject this + * pending interrupt into the guest, so the guest will not miss + * an interrupt, although may get an extra unwanted interrupt. + */ + if (kvm_notify_irqfd_resampler(ioapic->kvm, KVM_IRQCHIP_IOAPIC, index)) + ioapic->irr &= ~(1 << index); + else + ioapic_service(ioapic, index, false); + } if (e->fields.delivery_mode == APIC_DM_FIXED) { struct kvm_lapic_irq irq; |