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kvm/eventfd: Use sequence counter with associated spinlock 

A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lkml.kernel.org/r/20200720155530.1173732-24-a.darwish@linutronix.de
zero-sugar-mainline-defconfig
Ahmed S. Darwish 2020-07-20 17:55:29 +02:00 committed by Peter Zijlstra
parent 2ca97ac8bd
commit 5c73b9a2b1
2 changed files with 2 additions and 2 deletions
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2
include/linux/kvm_irqfd.h
View File

@ -42,7 +42,7 @@ struct kvm_kernel_irqfd {
wait_queue_entry_t wait;
/* Update side is protected by irqfds.lock */
struct kvm_kernel_irq_routing_entry irq_entry;
seqcount_t irq_entry_sc;
seqcount_spinlock_t irq_entry_sc;
/* Used for level IRQ fast-path */
int gsi;
struct work_struct inject;

2
virt/kvm/eventfd.c
View File

@ -303,7 +303,7 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
INIT_LIST_HEAD(&irqfd->list);
INIT_WORK(&irqfd->inject, irqfd_inject);
INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
seqcount_init(&irqfd->irq_entry_sc);
seqcount_spinlock_init(&irqfd->irq_entry_sc, &kvm->irqfds.lock);
f = fdget(args->fd);
if (!f.file) {