Use the recently introduced call_srcu_expedited() when freeing the old I/O bug during device registration to avoid triggering a non-expedited grace period. Delaying the freeing of the object by a full grace period is a complete non-issue, but the grace period also gets transferred to future synchronizations, e.g. to the synchronize_srcu_expedited() invocation in kvm_swap_active_memslots(). For micro-VM use cases, effectively transferring the non-expedited grace period to memslot updates results in a meaningful delay in overall boot time. E.g. with a CONFIG_HZ=100 kernel, the sync triggers a ~20ms delay, increasing boot times by 15% or more. Fixes: 7d9a0273c459 ("KVM: Avoid synchronize_srcu() in kvm_io_bus_register_dev()") Reported-by: Nikita Kalyazin Closes: https://lore.kernel.org/all/a84ddba8-12da-489a-9dd1-ccdf7451a1ba@amazon.com Cc: Keir Fraser Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 9faf70ccae7a..ceaf08a03428 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -6021,7 +6021,7 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, memcpy(new_bus->range + i + 1, bus->range + i, (bus->dev_count - i) * sizeof(struct kvm_io_range)); rcu_assign_pointer(kvm->buses[bus_idx], new_bus); - call_srcu(&kvm->srcu, &bus->rcu, __free_bus); + call_srcu_expedited(&kvm->srcu, &bus->rcu, __free_bus); return 0; } -- 2.53.0.473.g4a7958ca14-goog