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KVM: KVM Steal time guest/host interface

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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>
This commit is contained in:
Glauber Costa 2011-07-11 15:28:13 -04:00 committed by Avi Kivity
parent 4b6b35f55c
commit 9ddabbe72e
2 changed files with 43 additions and 0 deletions
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34
Documentation/virtual/kvm/msr.txt
View File

@ -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.

9
arch/x86/include/asm/kvm_para.h
View File

@ -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