linux-kernel - [PATCH v9 15/18] KVM: s390: pv: api documentation for asynchronous destroy

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Date:   Wed, 30 Mar 2022 14:26:02 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     kvm@...r.kernel.org
Cc:     borntraeger@...ibm.com, frankja@...ux.ibm.com, thuth@...hat.com,
        pasic@...ux.ibm.com, david@...hat.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, scgl@...ux.ibm.com,
        mimu@...ux.ibm.com, nrb@...ux.ibm.com
Subject: [PATCH v9 15/18] KVM: s390: pv: api documentation for asynchronous destroy

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

Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
---
 Documentation/virt/kvm/api.rst | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 9f3172376ec3..52ba1c52ae3c 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5010,11 +5010,13 @@ 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 prepared for asynchonous teardown
+  with KVM_PV_ASYNC_DISABLE_PREPARE and not actually torn down with
+  KVM_PV_ASYNC_DISABLE, 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
@@ -5027,6 +5029,23 @@ 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_DISABLE_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. If a protected VM had
+  already been prepared without starting the asynchronous teardown process,
+  this call will fail. In that case, the userspace process should issue a
+  normal KVM_PV_DISABLE.
+
+KVM_PV_ASYNC_DISABLE
+  Tear down the protected VM previously prepared for asynchronous teardown.
+  The resources that had been set aside will be freed asynchronously 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.
+
 4.126 KVM_X86_SET_MSR_FILTER
 ----------------------------
 
-- 
2.34.1