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It is useful to be able to do read-only traversal of the list of all the registered irqfd resamplers without locking the resampler_lock mutex. In particular, we are going to traverse it to search for a resampler registered for the given irq of an irqchip, and that will be done with an irqchip spinlock (ioapic->lock) held, so it is undesirable to lock a mutex in this context. So turn this list into an RCU list. For protecting the read side, reuse kvm->irq_srcu which is already used for protecting a number of irq related things (kvm->irq_routing, irqfd->resampler->list, kvm->irq_ack_notifier_list, kvm->arch.mask_notifier_list). Signed-off-by: Dmytro Maluka <dmy@semihalf.com> Message-Id: <20230322204344.50138-2-dmy@semihalf.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
64 lines
2 KiB
C
64 lines
2 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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*
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* irqfd: Allows an fd to be used to inject an interrupt to the guest
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* Credit goes to Avi Kivity for the original idea.
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*/
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#ifndef __LINUX_KVM_IRQFD_H
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#define __LINUX_KVM_IRQFD_H
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#include <linux/kvm_host.h>
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#include <linux/poll.h>
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/*
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* Resampling irqfds are a special variety of irqfds used to emulate
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* level triggered interrupts. The interrupt is asserted on eventfd
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* trigger. On acknowledgment through the irq ack notifier, the
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* interrupt is de-asserted and userspace is notified through the
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* resamplefd. All resamplers on the same gsi are de-asserted
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* together, so we don't need to track the state of each individual
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* user. We can also therefore share the same irq source ID.
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*/
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struct kvm_kernel_irqfd_resampler {
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struct kvm *kvm;
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/*
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* List of resampling struct _irqfd objects sharing this gsi.
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* RCU list modified under kvm->irqfds.resampler_lock
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*/
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struct list_head list;
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struct kvm_irq_ack_notifier notifier;
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/*
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* Entry in list of kvm->irqfd.resampler_list. Use for sharing
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* resamplers among irqfds on the same gsi.
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* RCU list modified under kvm->irqfds.resampler_lock
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*/
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struct list_head link;
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};
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struct kvm_kernel_irqfd {
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/* Used for MSI fast-path */
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struct kvm *kvm;
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wait_queue_entry_t wait;
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/* Update side is protected by irqfds.lock */
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struct kvm_kernel_irq_routing_entry irq_entry;
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seqcount_spinlock_t irq_entry_sc;
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/* Used for level IRQ fast-path */
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int gsi;
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struct work_struct inject;
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/* The resampler used by this irqfd (resampler-only) */
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struct kvm_kernel_irqfd_resampler *resampler;
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/* Eventfd notified on resample (resampler-only) */
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struct eventfd_ctx *resamplefd;
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/* Entry in list of irqfds for a resampler (resampler-only) */
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struct list_head resampler_link;
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/* Used for setup/shutdown */
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struct eventfd_ctx *eventfd;
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struct list_head list;
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poll_table pt;
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struct work_struct shutdown;
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struct irq_bypass_consumer consumer;
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struct irq_bypass_producer *producer;
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};
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#endif /* __LINUX_KVM_IRQFD_H */
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