Right now the semaphore is only used to signal that a vcpu entered KVM_RUN (not necessarly in guest mode, could be also blocked/halted). Later it will be used by specific ioctls (writers) to wait that all vcpus (readers) exit from KVM_RUN. Signed-off-by: Emanuele Giuseppe Esposito <eesposit@xxxxxxxxxx> --- virt/kvm/kvm_main.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index c080b93edc0d..ae0240928a4a 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -119,6 +119,8 @@ static const struct file_operations stat_fops_per_vm; static struct file_operations kvm_chardev_ops; +static DECLARE_RWSEM(memory_transaction); + static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl, unsigned long arg); #ifdef CONFIG_KVM_COMPAT @@ -4074,7 +4076,19 @@ static long kvm_vcpu_ioctl(struct file *filp, synchronize_rcu(); put_pid(oldpid); } + /* + * Notify that a vcpu wants to run, and thus could be reading + * memslots. + * If KVM_KICK_ALL_RUNNING_VCPUS runs afterwards, it will have + * to wait that KVM_RUN exited and up_read() is called. + * If KVM_KICK_ALL_RUNNING_VCPUS already returned but + * KVM_RESUME_ALL_KICKED_VCPUS didn't start yet, then there + * is a request pending for the vcpu that will cause it to + * exit KVM_RUN. + */ + down_read(&memory_transaction); r = kvm_arch_vcpu_ioctl_run(vcpu); + up_read(&memory_transaction); trace_kvm_userspace_exit(vcpu->run->exit_reason, r); break; } -- 2.31.1
