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

Glauber Costa
2011-06-13T23:31:32Z

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@redhat.com>
CC: Rik van Riel <riel@redhat.com>
CC: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Avi Kivity <avi@redhat.com>
CC: Anthony Liguori <aliguori@us.ibm.com>
CC: Eric B Munson <emunson@mgebm.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