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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 <sinisterpatrician@gmail.com>
Link: https://lore.kernel.org/r/20200501223624.GA25826@josh-ZenBook
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Joshua Abraham 2020-05-01 18:36:24 -04:00 committed by Jonathan Corbet
parent 094d6dc562
commit 35c5999005
1 changed files with 7 additions and 5 deletions
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12
Documentation/virt/kvm/api.rst
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@ -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