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authorDavid Woodhouse <dwmw@amazon.co.uk>2021-03-01 12:53:09 +0000
committerPaolo Bonzini <pbonzini@redhat.com>2021-03-02 14:30:54 -0500
commit30b5c851af7991ad08abe90c1e7c31615fa98a1a (patch)
treeb8596021030db95f8825f0f947da71e004450491 /Documentation
parent7d7c5f76e54131ed05b057103b5278b6b852148b (diff)
KVM: x86/xen: Add support for vCPU runstate information
This is how Xen guests do steal time accounting. The hypervisor records the amount of time spent in each of running/runnable/blocked/offline states. In the Xen accounting, a vCPU is still in state RUNSTATE_running while in Xen for a hypercall or I/O trap, etc. Only if Xen explicitly schedules does the state become RUNSTATE_blocked. In KVM this means that even when the vCPU exits the kvm_run loop, the state remains RUNSTATE_running. The VMM can explicitly set the vCPU to RUNSTATE_blocked by using the KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT attribute, and can also use KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST to retrospectively add a given amount of time to the blocked state and subtract it from the running state. The state_entry_time corresponds to get_kvmclock_ns() at the time the vCPU entered the current state, and the total times of all four states should always add up to state_entry_time. Co-developed-by: Joao Martins <joao.m.martins@oracle.com> Signed-off-by: Joao Martins <joao.m.martins@oracle.com> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Message-Id: <20210301125309.874953-2-dwmw2@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/virt/kvm/api.rst41
1 files changed, 41 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 359435d4e417..1a2b5210cdbf 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -4878,6 +4878,14 @@ see KVM_XEN_HVM_SET_ATTR above.
union {
__u64 gpa;
__u64 pad[4];
+ struct {
+ __u64 state;
+ __u64 state_entry_time;
+ __u64 time_running;
+ __u64 time_runnable;
+ __u64 time_blocked;
+ __u64 time_offline;
+ } runstate;
} u;
};
@@ -4890,6 +4898,31 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
Sets the guest physical address of an additional pvclock structure
for a given vCPU. This is typically used for guest vsyscall support.
+KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR
+ Sets the guest physical address of the vcpu_runstate_info for a given
+ vCPU. This is how a Xen guest tracks CPU state such as steal time.
+
+KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_CURRENT
+ Sets the runstate (RUNSTATE_running/_runnable/_blocked/_offline) of
+ the given vCPU from the .u.runstate.state member of the structure.
+ KVM automatically accounts running and runnable time but blocked
+ and offline states are only entered explicitly.
+
+KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_DATA
+ Sets all fields of the vCPU runstate data from the .u.runstate member
+ of the structure, including the current runstate. The state_entry_time
+ must equal the sum of the other four times.
+
+KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST
+ This *adds* the contents of the .u.runstate members of the structure
+ to the corresponding members of the given vCPU's runstate data, thus
+ permitting atomic adjustments to the runstate times. The adjustment
+ to the state_entry_time must equal the sum of the adjustments to the
+ other four times. The state field must be set to -1, or to a valid
+ runstate value (RUNSTATE_running, RUNSTATE_runnable, RUNSTATE_blocked
+ or RUNSTATE_offline) to set the current accounted state as of the
+ adjusted state_entry_time.
+
4.130 KVM_XEN_VCPU_GET_ATTR
---------------------------
@@ -4902,6 +4935,9 @@ KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO
Allows Xen vCPU attributes to be read. For the structure and types,
see KVM_XEN_VCPU_SET_ATTR above.
+The KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADJUST type may not be used
+with the KVM_XEN_VCPU_GET_ATTR ioctl.
+
5. The kvm_run structure
========================
@@ -6666,6 +6702,7 @@ PVHVM guests. Valid flags are::
#define KVM_XEN_HVM_CONFIG_HYPERCALL_MSR (1 << 0)
#define KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL (1 << 1)
#define KVM_XEN_HVM_CONFIG_SHARED_INFO (1 << 2)
+ #define KVM_XEN_HVM_CONFIG_RUNSTATE (1 << 2)
The KVM_XEN_HVM_CONFIG_HYPERCALL_MSR flag indicates that the KVM_XEN_HVM_CONFIG
ioctl is available, for the guest to set its hypercall page.
@@ -6680,3 +6717,7 @@ KVM_XEN_HVM_SET_ATTR, KVM_XEN_HVM_GET_ATTR, KVM_XEN_VCPU_SET_ATTR and
KVM_XEN_VCPU_GET_ATTR ioctls, as well as the delivery of exception vectors
for event channel upcalls when the evtchn_upcall_pending field of a vcpu's
vcpu_info is set.
+
+The KVM_XEN_HVM_CONFIG_RUNSTATE flag indicates that the runstate-related
+features KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR/_CURRENT/_DATA/_ADJUST are
+supported by the KVM_XEN_VCPU_SET_ATTR/KVM_XEN_VCPU_GET_ATTR ioctls.