linux-kernel - [PATCH v2 6/6] Describe KVM_MSR_STEAL

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Date:	Fri, 28 Jan 2011 14:52:20 -0500
From:	Glauber Costa <glommer@...hat.com>
To:	kvm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, aliguori@...ibm.com
Subject: [PATCH v2 6/6] Describe KVM_MSR_STEAL_TIME

This patch adds documentation about usage of the newly
introduced KVM_MSR_STEAL_TIME.

Signed-off-by: Glauber Costa <glommer@...hat.com>
---
 Documentation/kvm/msr.txt |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/Documentation/kvm/msr.txt b/Documentation/kvm/msr.txt
index d079aed..7a2d223 100644
--- a/Documentation/kvm/msr.txt
+++ b/Documentation/kvm/msr.txt
@@ -185,3 +185,35 @@ MSR_KVM_ASYNC_PF_EN: 0x4b564d02
 
 	Currently type 2 APF will be always delivered on the same vcpu as
 	type 1 was, but guest should not rely on that.
+
+MSR_KVM_STEAL_TIME: 0x4b564d03
+
+	data: 4-byte alignment physical address of a memory area which must be
+	in guest RAM, plus an enable bit in bit 0. This memory is expected to
+	hold a copy of the following structure:
+
+	struct kvm_steal_time {
+	  	__u64 steal;
+ 		__u32 version;
+ 		__u32 flags;
+	 	__u32 pad[6];
+	}
+
+	whose data will be filled in by the hypervisor periodically. Only one
+	write, or registration, is needed for each VCPU. The interval between
+	updates of this structure is arbitrary and implementation-dependent.
+	The hypervisor may update this structure at any time it sees fit until
+	anything with bit0 == 0 is written to it.
+
+	Fields have the following meanings:
+
+		version: guest has to check version before and after grabbing
+		time information and check that they are both equal and even.
+		An odd version indicates an in-progress update.
+
+		flags: At this point, always zero. May be used to indicate
+		changes in this structure in the future.
+
+		steal: the amount of time in which this vCPU did not run, in
+		nanoseconds.
+
-- 
1.7.2.3

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