On 02/16/2012 10:19 PM, Eric B Munson wrote: > Now that we have a flag that will tell the guest it was suspended, create an > interface for that communication using a KVM ioctl. > +4.70 KVM_KVMCLOCK_CTRL > + > +Capability: KVM_CAP_KVMCLOCK_CTRL > +Architectures: Any that implement pvclocks (currently x86 only) > +Type: vcpu ioctl > +Parameters: None > +Returns: 0 on success, -1 on error > + > +This signals to the host kernel that the specified guest is being paused by > +userspace. The host will set a flag in the pvclock structure that is checked > +from the soft lockup watchdog. The flag is part of the pvclock structure that > +is shared between guest and host, specifically the second bit of the flags > +field of the pvclock_vcpu_time_info structure. It will be set exclusively by > +the host and read/cleared exclusively by the guest. The guest operation of > +checking and clearing the flag must an atomic operation so use of the function > +check_and_clear_guest_paused() is encouraged, but it could also be done with > +load-link/store-conditional. There are two cases where the guest will clear > +the flag: when the soft lockup watchdog timer resets itself or when a soft > +lockup is detected. This ioctl can be called any time after pausing > +the vcpu, but before it is resumed. > + > Sorry to see this go into v15, but this splits the pvclock abi documentation into two pieces. Please update the master in msr.txt. Also don't use guest terms (like check_and_clear_guest_paused()) - this documentation should be usable by other OS writers without resorting to reading the Linux kernel source. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
