[PATCH 4/4] docs: add s390-pv documentation

Boris Fiuczynski fiuczy at linux.ibm.com
Wed May 19 17:40:53 UTC 2021

Add documentation for launch security type s390-pv.

Signed-off-by: Boris Fiuczynski <fiuczy at linux.ibm.com>
 docs/formatdomain.rst              |  7 ++++
 docs/kbase/s390_protected_virt.rst | 55 +++++++++++++++++++++++++-----
 2 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index fa5c14febc..635fd5a55f 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -8044,6 +8044,13 @@ Note: DEA/TDEA is synonymous with DES/TDES.
 Launch Security
+Specifying ``<launchSecurity type='s390-pv'\>`` in an s390 VM prepares for
+running the guest in protected virtualization secure mode, also known as
+IBM Secure Execution. For more required host and guest preparation steps, see
+`Protected Virtualization on s390 <kbase/s390_protected_virt.html>`__
+:since:`Since 7.4.0`
 The contents of the ``<launchSecurity type='sev'>`` element is used to provide
 the guest owners input used for creating an encrypted VM using the AMD SEV
 feature (Secure Encrypted Virtualization). SEV is an extension to the AMD-V
diff --git a/docs/kbase/s390_protected_virt.rst b/docs/kbase/s390_protected_virt.rst
index 1718a556d4..5c9ce0e21c 100644
--- a/docs/kbase/s390_protected_virt.rst
+++ b/docs/kbase/s390_protected_virt.rst
@@ -127,10 +127,13 @@ Protected virtualization guests support I/O using virtio devices.
 As the virtio data structures of secure guests are not accessible
 by the host, it is necessary to use shared memory ('bounce buffers').
-To enable virtio devices to use shared buffers, it is necessary
-to configure them with platform_iommu enabled. This can done by adding
-``iommu='on'`` to the driver element of a virtio device definition in the
-guest's XML, e.g.
+Since libvirt 7.4.0 the
+`<launchSecurity> <https://libvirt.org/formatdomain.html#launchSecurity>`__
+element with type ``s390-pv`` should be used on protected virtualization guests.
+Without ``launchSecurity`` you must enable all virtio devices to use shared
+buffers by configuring them with platform_iommu enabled.
+This can done by adding ``iommu='on'`` to the driver element of a virtio
+device definition in the guest's XML, e.g.
@@ -140,8 +143,10 @@ guest's XML, e.g.
      <driver name='vhost' iommu='on'/>
-It is mandatory to define all virtio bus devices in this way to
-prevent the host from attempting to access protected memory.
+Unless you are using ``launchSecurity`` you must define all virtio bus
+devices in this way to prevent the host from attempting to access
+protected memory.
 Ballooning will not work and is fenced by QEMU. It should be
 disabled by specifying
@@ -158,8 +163,42 @@ allocated 2K entries. A commonly used value for swiotlb is 262144.
 Example guest definition
-Minimal domain XML for a protected virtualization guest, essentially
-it's mostly about the ``iommu`` property
+Minimal domain XML for a protected virtualization guest with
+the ``launchSecurity`` element of type ``s390-pv``
+   <domain type='kvm'>
+     <name>protected</name>
+     <memory unit='KiB'>2048000</memory>
+     <currentMemory unit='KiB'>2048000</currentMemory>
+     <vcpu>1</vcpu>
+     <os>
+       <type arch='s390x'>hvm</type>
+     </os>
+     <cpu mode='host-model'/>
+     <devices>
+       <disk type='file' device='disk'>
+         <driver name='qemu' type='qcow2' cache='none' io='native'>
+         <source file='/var/lib/libvirt/images/protected.qcow2'/>
+         <target dev='vda' bus='virtio'/>
+       </disk>
+       <interface type='network'>
+         <source network='default'/>
+         <model type='virtio'/>
+       </interface>
+       <console type='pty'/>
+       <memballoon model='none'/>
+     </devices>
+     <launchSecurity type='s390-pv'/>
+   </domain>
+Example guest definition without launchSecurity
+Minimal domain XML for a protected virtualization guest using the
+``iommu='on'`` setting for each virtio device.

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