linux-kernel - Re: [PATCH] docs: kvm: Fix KVM_KVMCLOCK

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Date:   Fri, 1 May 2020 17:10:40 -0400
From:   Joshua Abraham <j.abraham1776@...il.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     pbonzini@...hat.com, corbet@....net, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        j.abraham1776@...il.com
Subject: Re: [PATCH] docs: kvm: Fix KVM_KVMCLOCK_CTRL API doc

On Fri, May 01, 2020 at 01:51:06PM -0700, Sean Christopherson wrote:
> I don't disagree, but simply doing s/host/guest yields a misleading
> sentence and inconsistencies with the rest of the paragraph.

I see your point. Would this wording be clearer:

"This ioctl sets a flag accessible to the guest indicating that it has been
paused from 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 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
after pausing the vcpu, but before it is resumed."