KVM: KVM Steal time guest/host interface

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

diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt
index d079aed..5031780 100644 (file)
--- a/Documentation/virtual/kvm/msr.txt
+++ b/Documentation/virtual/kvm/msr.txt
@@ -185,3 +185,37 @@ 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[12];
+       }
+
+       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: a sequence counter. In other words, guest has to check
+               this field before and after grabbing time information and make
+               sure 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. Time during which the vcpu is idle, will not be
+               reported as steal time.

diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index d6cd79b..65f8bb9 100644 (file)
--- 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[12];
+};
 
 #define KVM_MAX_MMU_OP_BATCH           32