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KVM: x86/xen: Add support for vCPU runstate information

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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>
This commit is contained in:
David Woodhouse
2021-03-01 12:53:09 +00:00
committed by Paolo Bonzini
parent 7d7c5f76e5
commit 30b5c851af
7 changed files with 553 additions and 5 deletions
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41
Documentation/virt/kvm/api.rst
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@@ -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.