linux-kernel - Re: [PATCH 3/4 V13] Add ioctl for KVM_KVMCLOCK

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Date:	Thu, 16 Feb 2012 16:11:40 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Eric B Munson <emunson@...bm.net>
CC:	mingo@...hat.com, hpa@...or.com, ryanh@...ux.vnet.ibm.com,
	aliguori@...ibm.com, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4 V13] Add ioctl for KVM_KVMCLOCK_CTRL

On 02/08/2012 05:07 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.
>
> +
> +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.  

This needs to be expanded.  There is a protocol between the host and
guest that needs to be documented, including the requirement to use a
single instruction (or ll/sc) to clear the flag.  See
Documentation/virtual/kvm/msr.txt

> This ioctl can be called during pause or
> +unpause.
> +

After pausing the vcpu, but before resuming it.


-- 
error compiling committee.c: too many arguments to function

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