linux-kernel - Re: [PATCH v14 2/6] KVM: s390: pv: api documentation for asynchronous destroy

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Date:   Tue, 4 Oct 2022 15:43:54 +0200
From:   Steffen Eiden <seiden@...ux.ibm.com>
To:     Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org
Cc:     borntraeger@...ibm.com, frankja@...ux.ibm.com, thuth@...hat.com,
        david@...hat.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, scgl@...ux.ibm.com, nrb@...ux.ibm.com
Subject: Re: [PATCH v14 2/6] KVM: s390: pv: api documentation for asynchronous
 destroy



On 9/30/22 16:01, Claudio Imbrenda wrote:
> Add documentation for the new commands added to the KVM_S390_PV_COMMAND
> ioctl.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> Reviewed-by: Nico Boehr <nrb@...ux.ibm.com>LGTM.

Reviewed-by: Steffen Eiden <seiden@...ux.ibm.com>

> ---
>   Documentation/virt/kvm/api.rst | 37 ++++++++++++++++++++++++++++++----
>   1 file changed, 33 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index abd7c32126ce..5775e5fbfd18 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -5161,10 +5161,13 @@ 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.
> +  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. If a
> +  previous protected VM had been prepared for asynchonous teardown with
> +  KVM_PV_ASYNC_CLEANUP_PREPARE and not subsequently torn down with
> +  KVM_PV_ASYNC_CLEANUP_PERFORM, it will be torn down in this call
> +  together with the current protected VM.
>   
>   KVM_PV_VM_SET_SEC_PARMS
>     Pass the image header from VM memory to the Ultravisor in
> @@ -5287,6 +5290,32 @@ KVM_PV_DUMP
>       authentication tag all of which are needed to decrypt the dump at a
>       later time.
>   
> +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 prepared for asynchronous teardown at any time. If
> +  a protected VM had already been prepared for teardown without
> +  subsequently calling KVM_PV_ASYNC_CLEANUP_PERFORM, 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_PREPARE can be called again as soon
> +  as cleanup starts, i.e. before KVM_PV_ASYNC_CLEANUP_PERFORM finishes.
> +
> +KVM_PV_ASYNC_CLEANUP_PERFORM
> +  Tear down the protected VM previously prepared for teardown 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, including the ones whose teardown was interrupted by
> +  process termination.
> +
>   
>   4.126 KVM_X86_SET_MSR_FILTER
>   ----------------------------