I've mailed out cl/181496858 to create this feature on the server side.
It's easy to access this feature on the Chrome side. How should this feature be accessed by the vm_tools? What kind of interface do we need to expose this feature to other processes?

Tim, My first thought would be to do it via D-Bus (standard way to talk between Chrome browser and ChromeOS daemons)...but that seems like it might be overkill. You may want to ask on the chrome-os mailing list if anybody else has used Finch to control things at the ChromeOS level and how they did it.

Change 181496858 renamed cl/181552262 and submitted.

Let's plan to enable this early next week (Jan 22) so it's after M65 branch.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/system_api/+/5c8aa4d8a30e89added6423a242360225661c554

commit 5c8aa4d8a30e89added6423a242360225661c554
Author: Tim Zheng <timzheng@google.com>
Date: Fri Jan 19 08:29:46 2018

Add Chrome Features DBus interface.

This CL contains the constants for the DBus interface. Actuall
implementation will follow in a subsequent CL upon DEP update.

BUG= chromium:800120 
TEST=compile locally

Change-Id: Ia225bb343ad3b034a1e23ee489080910e8303e93
Reviewed-on: https://chromium-review.googlesource.com/874610
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Tim Zheng <timzheng@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Jeffrey Kardatzke <jkardatzke@google.com>

[modify] https://crrev.com/5c8aa4d8a30e89added6423a242360225661c554/dbus/service_constants.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/765ed824aed987178f1f826712feb8cb406b12cc

commit 765ed824aed987178f1f826712feb8cb406b12cc
Author: Tim Zheng <timzheng@google.com>
Date: Sat Jan 20 01:56:26 2018

Roll src/third_party/cros_system_api/ 15e1a4681..5c8aa4d8a (5 commits)

https://chromium.googlesource.com/chromiumos/platform/system_api.git/+log/15e1a468124f..5c8aa4d8a30e

$ git log 15e1a4681..5c8aa4d8a --date=short --no-merges --format='%ad %ae %s'
2018-01-18 timzheng Add Chrome Features DBus interface.
2018-01-17 allenvic smbprovider: Add CreateFileOptions and TruncateOptions protobuf
2018-01-15 hashimoto obb-mounter: Add OBB mounter constants
2018-01-10 tnagel system_api: Drop unused *EnrollmentState
2018-01-16 baileyberro smbprovider: Add DeleteEntryOptions protobuf to systemapi

Created with:
  roll-dep src/third_party/cros_system_api

TEST=roll-dep generated chang.

Bug:  chromium:800120 
Change-Id: Iec11c430f9a608f4b9719740c7d7fcf35e5d23f4
Reviewed-on: https://chromium-review.googlesource.com/877181
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530728}
[modify] https://crrev.com/765ed824aed987178f1f826712feb8cb406b12cc/DEPS

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/78822b3eb0da819f3a87ec2a83177cab4e86771a

commit 78822b3eb0da819f3a87ec2a83177cab4e86771a
Author: Tim Zheng <timzheng@google.com>
Date: Sun Jan 21 04:48:13 2018

Add a DBus interface to query Crostini enablement.

This CL exposes a DBus method call IsCrostiniEnabled that returns a
boolean indicating whether Crostini should be enabled on this machine.

BUG= chromium:800120 
TEST=dbus-send is working on chrome OS.

Change-Id: I577380c396ea3d8872c3ab58c0455cdc4cc95df9
Reviewed-on: https://chromium-review.googlesource.com/874717
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530767}
[modify] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chrome/browser/chromeos/BUILD.gn
[modify] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
[add] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chrome/browser/chromeos/dbus/finch_features_service_provider_delegate.cc
[add] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chrome/browser/chromeos/dbus/finch_features_service_provider_delegate.h
[modify] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chrome/common/chrome_features.cc
[modify] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chrome/common/chrome_features.h
[modify] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chromeos/BUILD.gn
[add] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chromeos/dbus/services/chrome_features_service_provider.cc
[add] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chromeos/dbus/services/chrome_features_service_provider.h
[add] https://crrev.com/78822b3eb0da819f3a87ec2a83177cab4e86771a/chromeos/dbus/services/org.chromium.ChromeFeaturesService.conf

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/2a067c7ef501cedf8361041387df8b80d3a3a29e

commit 2a067c7ef501cedf8361041387df8b80d3a3a29e
Author: Tim Zheng <timzheng@google.com>
Date: Mon Jan 22 21:13:31 2018

crosh: Gate the "vmc" command by a Chrome Feature.

This change makes command "vmc" available only when Chrome Feature
"Crostini" is set. This is used to enable Crostini dogfood while prevent
others to use it for now.

BUG= chromium:800120 
TEST=manually tested.

Change-Id: I49320464a3531130987335793a94b87caa60456a
Reviewed-on: https://chromium-review.googlesource.com/875163
Commit-Ready: Tim Zheng <timzheng@chromium.org>
Tested-by: Tim Zheng <timzheng@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/2a067c7ef501cedf8361041387df8b80d3a3a29e/crosh/crosh

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/721782f940de29d7bee2d532e6628539e64242e3

commit 721782f940de29d7bee2d532e6628539e64242e3
Author: Tim Zheng <timzheng@google.com>
Date: Tue Jan 23 06:21:08 2018

Add Crostini experiment to fieldtrial testing.

This enables project Crostini, running Linux VM on chrome OS, for
Chromium developer builds.

BUG= chromium:800120 
TEST=Locally tested on my developer build.

Change-Id: Ibf6028cba6f140fc5730b9ea3a25e667d263ad6f
Reviewed-on: https://chromium-review.googlesource.com/879173
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531168}
[modify] https://crrev.com/721782f940de29d7bee2d532e6628539e64242e3/testing/variations/fieldtrial_testing_config.json

We also have users with devices that are not Google assets. We want to keep eve-kvm board enabled always.

remind me ... finch doesn't have the ability to filter based on device details ?

I submitted another Finch config to enable eve-kvm.
https://critique.corp.google.com/#review/183151000

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a140b7172c1bb4290f7d9c5df31a799d4b83e257

commit a140b7172c1bb4290f7d9c5df31a799d4b83e257
Author: Tim Zheng <timzheng@google.com>
Date: Fri Feb 09 18:55:22 2018

New device policy to allow Linux VMs on Chrome OS.

If the policy is unset or set to true, running Linux VMs on Chrome OS is
allowed. The unset is allowed means non-managed devices are allowed.

At this time, in order for Linux VMs to run, the Finch experiment also
needs to be enabled. After this feature is fully launched, the Finch
control logic will be removed.

BUG= chromium:800120 
TEST=manually tested on an eve device with dbus-send results verified.

Change-Id: Iceec3341540edce5b815cc74aea0b56e12c35252
Reviewed-on: https://chromium-review.googlesource.com/899767
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Pavol Marko <pmarko@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535769}
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chrome/browser/chromeos/BUILD.gn
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chrome/browser/chromeos/dbus/finch_features_service_provider_delegate.cc
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chrome/browser/chromeos/settings/device_settings_provider.cc
[add] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chrome/browser/chromeos/virtual_machines/virtual_machines_util.cc
[add] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chrome/browser/chromeos/virtual_machines/virtual_machines_util.h
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chrome/test/data/policy/policy_test_cases.json
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chromeos/settings/cros_settings_names.cc
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/chromeos/settings/cros_settings_names.h
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/components/policy/proto/chrome_device_policy.proto
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/components/policy/resources/policy_templates.json
[modify] https://crrev.com/a140b7172c1bb4290f7d9c5df31a799d4b83e257/tools/metrics/histograms/enums.xml

I submitted this CL to restrict dogfood to canary and dev channels only.
https://critique.corp.google.com/#review/185587639

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/28aabeb973ae38fda1791613d6e435fb0ec7ce8a

commit 28aabeb973ae38fda1791613d6e435fb0ec7ce8a
Author: Dylan Reid <dgreid@chromium.org>
Date: Wed Feb 14 01:41:31 2018

eve: Enable KVM host functionality

Enabling the kvm_host use flag on eve installs the VM management tools.
This does not enable using the tools, that is still behind a finch
experiment.

TEST=build an eve image and confirm crosvm is installed.
BUG= 800120 

Change-Id: I7f5cb6218e2fa1d93dbe57c351e1b404258cf458
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/915023
Reviewed-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>

[modify] https://crrev.com/28aabeb973ae38fda1791613d6e435fb0ec7ce8a/overlay-eve/profiles/base/make.defaults

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5886332700869708024ff39b3452f4936776103c

commit 5886332700869708024ff39b3452f4936776103c
Author: Tim Zheng <timzheng@google.com>
Date: Wed Feb 28 00:20:46 2018

Change VirtualMachinesAllowed managed default.

Change the default to True for managed devices for now. This will enable
dogfood while the policy is in the process of being rolled out. The
feature can still be turned off by using the enterprise policy once
policy is rolled out in the backend.

BUG= chromium:800120 
TEST=manually tested with YAPS.

Change-Id: I441c77f896d185aefd7eeaf3b7ed89fd19b99a7d
Reviewed-on: https://chromium-review.googlesource.com/940182
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539597}
[modify] https://crrev.com/5886332700869708024ff39b3452f4936776103c/chrome/browser/chromeos/settings/device_settings_provider.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cbde4515a4e06d0ea9bf612f5fa7395984ffe094

commit cbde4515a4e06d0ea9bf612f5fa7395984ffe094
Author: Tim Zheng <timzheng@google.com>
Date: Fri Mar 02 04:50:59 2018

Update a comment on VirtualMachinesAllowed policy.

Update the comment to reflect a recent code change
https://chromium-review.googlesource.com/c/chromium/src/+/899767.
In proto ChromeDeviceSettingsProto from components/policy/proto/chrome_device_policy.proto, each device policy setting is represented as a proto buffer message which has a member field that holds the setting value. For example, for this policy, the outer message virtual_machines_allowed is type of VirtualMachinesAllowedProto which has a bool member virtual_machines_allowed. The default values for when the outer message is not set or when the outer message is set but the inner field is not set should be the same to avoid mistakes.
For VirtualMachinesAllowed, both default values are consistently True.

BUG= chromium:800120 
TEST=Comment change only.

Change-Id: I68c49b19bb5bcbf71a9d4573f6f96753e45fd290
Reviewed-on: https://chromium-review.googlesource.com/942343
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#540447}
[modify] https://crrev.com/cbde4515a4e06d0ea9bf612f5fa7395984ffe094/components/policy/resources/policy_templates.json

@timzheng when will you swap the default policy value back to false?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5a174c9b522a11d138af9c57111bc217805626be

commit 5a174c9b522a11d138af9c57111bc217805626be
Author: Tim Zheng <timzheng@google.com>
Date: Wed Mar 28 01:29:54 2018

Disable Finch control of virtual machines.

This disables controlling the running of virtual machines with Finch
configs. It is intended as a temp measure before Finch fixes its bug
that prevent configs from being pulled when Chrome starts.

BUG= chromium:800120 
TEST=manual test.

Change-Id: Ic1571f034361cafdd2f7565e665b7f21dca392bf
Reviewed-on: https://chromium-review.googlesource.com/982519
Reviewed-by: Dan Erat <derat@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546362}
[modify] https://crrev.com/5a174c9b522a11d138af9c57111bc217805626be/chrome/browser/chromeos/dbus/finch_features_service_provider_delegate.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9c29a858ddd6cb8341f88f29ceda15c993cebb0b

commit 9c29a858ddd6cb8341f88f29ceda15c993cebb0b
Author: Tim Zheng <timzheng@google.com>
Date: Thu Mar 29 00:54:37 2018

Enable virtual machines by version and channel.

BUG= chromium:800120 
TEST=manual test.

Change-Id: I1d05d5b8d75f8a4380820bcab2d09f0869adfce4
Reviewed-on: https://chromium-review.googlesource.com/985143
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546680}
[modify] https://crrev.com/9c29a858ddd6cb8341f88f29ceda15c993cebb0b/chrome/browser/chromeos/dbus/finch_features_service_provider_delegate.cc
[modify] https://crrev.com/9c29a858ddd6cb8341f88f29ceda15c993cebb0b/chrome/browser/chromeos/virtual_machines/virtual_machines_util.cc
[modify] https://crrev.com/9c29a858ddd6cb8341f88f29ceda15c993cebb0b/chrome/browser/chromeos/virtual_machines/virtual_machines_util.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0f059d935b029daf3c50b130560c55dbb22e171b

commit 0f059d935b029daf3c50b130560c55dbb22e171b
Author: Tim Zheng <timzheng@google.com>
Date: Tue Apr 03 18:52:31 2018

Update virtual machines allowed logic in app_list.

This is to keep up to date with the logic change that the DBus service
uses. The logic has changed to use hard coded release version and
channel due to a bug in Finch.

BUG= chromium:800120 
TESTED=manually tested.

Change-Id: Ic5c33d97c2100592732df4a0a14ab744197ec377
Reviewed-on: https://chromium-review.googlesource.com/987100
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547777}
[modify] https://crrev.com/0f059d935b029daf3c50b130560c55dbb22e171b/chrome/browser/ui/app_list/crostini/crostini_util.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/852d7040bfa75c7046902eeca97ded8e0670f121

commit 852d7040bfa75c7046902eeca97ded8e0670f121
Author: Tim Zheng <timzheng@google.com>
Date: Fri Apr 06 02:22:28 2018

Fix an error in a comment.

BUG= chromium:800120 
TEST=comment only change.

Change-Id: Ie3a5d99186419c6a11d3efac4e7b50ec459cf772
Reviewed-on: https://chromium-review.googlesource.com/999118
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548642}
[modify] https://crrev.com/852d7040bfa75c7046902eeca97ded8e0670f121/chromeos/dbus/services/chrome_features_service_provider.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b01f43894297a909872f1822592ac46c40b57c0c

commit b01f43894297a909872f1822592ac46c40b57c0c
Author: Maksim Ivanov <emaxx@chromium.org>
Date: Wed Apr 11 10:33:32 2018

Fix VirtualMachinesAllowed policy parsing for UI

Fix inconsistency in the code that parses this policy for the policy map
(which is used for the chrome://policy page). The code shouldn't pretend
to have the policy set (with the default value) when the enclosing proto
message is present but with the actual policy proto field unset.

Note that the fixed issue should have been a purely UI glitch - the
actual policy application wasn't affected.

BUG= chromium:800120 
TEST=none

Change-Id: I32d55dc6bfe64ec8b1cac7c090028f805c91560a
Reviewed-on: https://chromium-review.googlesource.com/986096
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549849}
[modify] https://crrev.com/b01f43894297a909872f1822592ac46c40b57c0c/chrome/browser/chromeos/policy/device_policy_decoder_chromeos.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f468cd062d5e0a170ee9d6cfc0c346fdd993b104

commit f468cd062d5e0a170ee9d6cfc0c346fdd993b104
Author: Tim Zheng <timzheng@google.com>
Date: Fri Apr 20 17:53:09 2018

Flip policy VirtualMachinesAllowed default value.

This change flip the default value of device policy for managed devices
only. When the device policy VirtualMachinesAllowed is not set for
managed devices, the default is now False.

Please note that this change doesn't modify the policy value for
unmanaged devices. It's always True.

BUG= chromium:800120 
TEST=Manual test with YAPS tool.

Change-Id: Iddcfc4ad818db5be076b05c23d0f51f960fef059
Reviewed-on: https://chromium-review.googlesource.com/1017308
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552381}
[modify] https://crrev.com/f468cd062d5e0a170ee9d6cfc0c346fdd993b104/chrome/browser/chromeos/settings/device_settings_provider.cc
[modify] https://crrev.com/f468cd062d5e0a170ee9d6cfc0c346fdd993b104/components/policy/resources/policy_templates.json

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2dd076606271402aa23c4562a721996f79b0776c

commit 2dd076606271402aa23c4562a721996f79b0776c
Author: Tim Zheng <timzheng@google.com>
Date: Thu Jun 14 17:13:22 2018

Update Crostini release version and channel.

We want to release to dev/canary for version 67 and 68 and to release to
all chanels since version 69.

The beta/stable release is pushed back from 68 to 69.
BUG= chromium:800120 
TEST=manual test.

Change-Id: I02851521a0b9266157be3c4eb510546637b538a1
Reviewed-on: https://chromium-review.googlesource.com/1100539
Reviewed-by: Dan Erat <derat@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567321}
[modify] https://crrev.com/2dd076606271402aa23c4562a721996f79b0776c/chrome/browser/chromeos/virtual_machines/virtual_machines_util.cc