linux-kernel - [PATCH v2 2/7] KVM-HDR: KVM Steal time implementation

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Date:	Thu, 16 Jun 2011 18:20:51 -0400
From:	Glauber Costa <glommer@...hat.com>
To:	kvm@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Avi Kivity <avi@...hat.com>,
	Anthony Liguori <aliguori@...ibm.com>,
	Eric B Munson <emunson@...bm.net>
Subject: [PATCH v2 2/7] KVM-HDR: KVM Steal time implementation

To implement steal time, we need the hypervisor to pass the guest information
about how much time was spent running other processes outside the VM.
This is per-vcpu, and using the kvmclock structure for that is an abuse
we decided not to make.

In this patchset, I am introducing a new msr, KVM_MSR_STEAL_TIME, that
holds the memory area address containing information about steal time

This patch contains the headers for it. I am keeping it separate to facilitate
backports to people who wants to backport the kernel part but not the
hypervisor, or the other way around.

Signed-off-by: Glauber Costa <glommer@...hat.com>
CC: Rik van Riel <riel@...hat.com>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
CC: Peter Zijlstra <peterz@...radead.org>
CC: Avi Kivity <avi@...hat.com>
CC: Anthony Liguori <aliguori@...ibm.com>
CC: Eric B Munson <emunson@...bm.net>
---
 Documentation/virtual/kvm/msr.txt |   33 +++++++++++++++++++++++++++++++++
 arch/x86/include/asm/kvm_para.h   |    9 +++++++++
 2 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt
index d079aed..79c12a7 100644
--- a/Documentation/virtual/kvm/msr.txt
+++ b/Documentation/virtual/kvm/msr.txt
@@ -185,3 +185,36 @@ 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: 64-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. Guest is required to make sure
+	this structure is initialized to zero.
+
+	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.
+
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index d6cd79b..ac306c4 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -21,6 +21,7 @@
  */
 #define KVM_FEATURE_CLOCKSOURCE2        3
 #define KVM_FEATURE_ASYNC_PF		4
+#define KVM_FEATURE_STEAL_TIME		5
 
 /* The last 8 bits are used to indicate how to interpret the flags field
  * in pvclock structure. If no bits are set, all flags are ignored.
@@ -35,6 +36,14 @@
 #define MSR_KVM_WALL_CLOCK_NEW  0x4b564d00
 #define MSR_KVM_SYSTEM_TIME_NEW 0x4b564d01
 #define MSR_KVM_ASYNC_PF_EN 0x4b564d02
+#define MSR_KVM_STEAL_TIME  0x4b564d03
+
+struct kvm_steal_time {
+	__u64 steal;
+	__u32 version;
+	__u32 flags;
+	__u32 pad[6];
+};
 
 #define KVM_MAX_MMU_OP_BATCH           32
 
-- 
1.7.3.4

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