[PATCH v12 14/18] KVM: s390: pv: api documentation for asynchronous destroy

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

Add documentation for the new commands added to the KVM_S390_PV_COMMAND
ioctl.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
---
 Documentation/virt/kvm/api.rst | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 11e00a46c610..24f91ae0e494 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5143,11 +5143,13 @@ KVM_PV_ENABLE
   =====      =============================
 
 KVM_PV_DISABLE
-
   Deregister the VM from the Ultravisor and reclaim the memory that
   had been donated to the Ultravisor, making it usable by the kernel
-  again.  All registered VCPUs are converted back to non-protected
-  ones.
+  again. All registered VCPUs are converted back to non-protected
+  ones. If a previous VM had been set aside for asynchonous teardown
+  with KVM_PV_ASYNC_CLEANUP_PREPARE and not actually torn down with
+  KVM_PV_ASYNC_CLEANUP_PERFORM, it will be torn down in this call
+  together with the current VM.
 
 KVM_PV_VM_SET_SEC_PARMS
   Pass the image header from VM memory to the Ultravisor in
@@ -5160,6 +5162,29 @@ KVM_PV_VM_VERIFY
   Verify the integrity of the unpacked image. Only if this succeeds,
   KVM is allowed to start protected VCPUs.
 
+KVM_PV_ASYNC_CLEANUP_PREPARE
+  Prepare the current protected VM for asynchronous teardown. Most
+  resources used by the current protected VM will be set aside for a
+  subsequent asynchronous teardown. The current protected VM will then
+  resume execution immediately as non-protected. There can be at most
+  one protected VM set aside at any time. If a protected VM had
+  already been set aside without starting the asynchronous teardown
+  process, this call will fail. In that case, the userspace process
+  should issue a normal KVM_PV_DISABLE. The resources set aside with
+  this call will need to be cleaned up with a subsequent call to
+  KVM_PV_ASYNC_CLEANUP_PERFORM or KVM_PV_DISABLE, otherwise they will
+  be cleaned up when KVM terminates.
+
+KVM_PV_ASYNC_CLEANUP_PERFORM
+  Tear down the protected VM previously set aside with
+  KVM_PV_ASYNC_CLEANUP_PREPARE. The resources that had been set aside
+  will be freed during the execution of this command. This PV command
+  should ideally be issued by userspace from a separate thread. If a
+  fatal signal is received (or the process terminates naturally), the
+  command will terminate immediately without completing, and the normal
+  KVM shutdown procedure will take care of cleaning up all remaining
+  protected VMs.
+
 4.126 KVM_X86_SET_MSR_FILTER
 ----------------------------
 
-- 
2.36.1