From: Joshua Abraham Date: Fri, 1 May 2020 22:36:24 +0000 (-0400) Subject: docs: kvm: Fix KVM_KVMCLOCK_CTRL API doc X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=35c59990058351a1c9efab9e49dd19c2e5579cfb;p=linux.git docs: kvm: Fix KVM_KVMCLOCK_CTRL API doc The KVM_KVMCLOCK_CTRL ioctl signals to supported KVM guests that the hypervisor has paused it. Update the documentation to reflect that the guest is notified by this API. Signed-off-by: Joshua Abraham Link: https://lore.kernel.org/r/20200501223624.GA25826@josh-ZenBook Signed-off-by: Jonathan Corbet --- diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index efbbe570aa9b7..d2c1cbce1018d 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -2572,13 +2572,15 @@ list in 4.68. :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 +This ioctl sets a flag accessible to the guest indicating that the specified +vCPU has been paused by the host 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 +checking and clearing the flag must be an atomic operation so load-link/store-conditional, or equivalent must be used. 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