diff --git a/CREDITS.md b/CREDITS.md
index 34ceb30..9c26d9a 100644
--- a/CREDITS.md
+++ b/CREDITS.md
@@ -29,3 +29,5 @@
 * Nikolay Dimitrov (nikidim) - Docker for Mac
 
 * Francisco de la Peña - libvirt XML file for macOS High Sierra
+
+* Christian Giliberto - libvirt XML tweaks
diff --git a/HighSierra/README.md b/HighSierra/README.md
index ef4c78e..7d690c5 100644
--- a/HighSierra/README.md
+++ b/HighSierra/README.md
@@ -7,7 +7,9 @@
 
 Known to work on:
 
-* Fedora 25 running on i7-6600U CPU.
+* Fedora 27 running on i7-6600U CPU.
+
+* Fedora 27 running on i7-5820K CPU.
 
 * Ubuntu 17.04 running on i5-6500 CPU.
 
diff --git a/macOS-HS-libvirt.xml b/macOS-HS-libvirt.xml
index 2f5719b..e08aaf2 100644
--- a/macOS-HS-libvirt.xml
+++ b/macOS-HS-libvirt.xml
@@ -1,10 +1,13 @@
+<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
 <!--
 	macos High Sierra libvirt XML configuration.
 
+        Run "virt-xml-validate macOS-HS-libvirt.xml" to validate this file.
+
 	You may hot-redirect USB with ease from GNOME Boxes and other goodies.
 
 	To install this file, you may place it at ~/.config/libvirt/qemu/
-	and run: virsh define --file macOS-HS-libvirt.xml --validate.
+	and run: virsh define macOS-HS-libvirt.xml.
 
 	This configuration has been tested in Fedora 27 with stock QEMU-KVM.
 
@@ -25,8 +28,15 @@
 		Change interface to <interface type='user'>
 		and remove the <source bridge='virbr0'/>
 		Or use virt-manager to edit this line instead of virsh edit.
+
+	Note: Default configuration caused severe clock problems
+	under Fedora 27 w/ i7-5820K. This is because Darwin uses
+	tsc (time since last tick) for time, and for me did not
+	fall back to rtc in the event of a clock mismatch with
+	libvirt's default time source. Therefore we must explicitly
+	give the clock a tsc timer for kvm to pass to the guest.
+	See comments on the <kvm> and <clock> attributes.
 -->
-<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
   <name>macos-high-sierra</name>
   <uuid>2aca0dd6-cec9-4717-9ab2-0b7b13d111c3</uuid>
   <title>macOS High Sierra</title>
@@ -40,6 +50,7 @@
   </os>
   <features>
     <acpi/>
+<!-- Note: On Fedora 27 w/ an i7-5820K CPU and repository QEMU version as of 27-Jan-2018, the guest experienced severe clock issues. If you encounter these issues, try changing this to <hidden state ='off'-->
     <kvm>
       <hidden state='on'/>
     </kvm>
@@ -58,6 +69,15 @@
     <feature policy='require' name='avx2'/>
     <feature policy='require' name='smep'/>
   </cpu>
+<!-- Note: To resolve clock issues experienced on Fedora 27 as described at top of file,
+     we need to add a timer. Replace the clock offset line with
+
+     <clock offset='utc'>
+       <timer name='tsc'/>
+     </clock>
+
+     Please remember to also change the kvm hidden state as well, as described above.
+-->
   <clock offset='utc'/>
   <on_poweroff>destroy</on_poweroff>
   <on_reboot>restart</on_reboot>