Re: [PATCH v6 28/28] docs/system/s390x: Add secure IPL documentation

[Thomas Huth <thuth@redhat.com>]

On 18/09/2025 01.21, Zhuoying Cai wrote:
> Add documentation for secure IPL
> 
> Signed-off-by: Collin Walling <walling@linux.ibm.com>
> Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com>
> ---
>   docs/system/s390x/secure-ipl.rst | 96 ++++++++++++++++++++++++++++++++
>   1 file changed, 96 insertions(+)
> 
> diff --git a/docs/system/s390x/secure-ipl.rst b/docs/system/s390x/secure-ipl.rst
> index 579b7b4993..110dea9fdd 100644
> --- a/docs/system/s390x/secure-ipl.rst
> +++ b/docs/system/s390x/secure-ipl.rst
> @@ -1,5 +1,21 @@
>   .. SPDX-License-Identifier: GPL-2.0-or-later
>   
> +s390 Secure IPL
> +===============
> +
> +Secure IPL, also known as secure boot, enables s390-ccw virtual machines to
> +verify the integrity of guest kernels.
> +
> +For technical details of this feature, see ``docs/specs/s390x-secure-ipl.rst``.
> +
> +This document explains how to use secure IPL with s390x in QEMU. It covers
> +new command line options for providing certificates and enabling secure IPL,
> +the different IPL modes (Normal, Audit, and Secure), and system requirements.
> +
> +A quickstart guide is provided to demonstrate how to generate certificates,
> +sign images, and start a guest in Secure Mode.
> +
> +
>   Secure IPL Command Line Options
>   ===============================
>   
> @@ -83,3 +99,83 @@ Configuration:
>                                  secure-boot=on, \
>                                  boot-certs.0.path=/.../qemu/certs, \
>                                  boot-certs.1.path=/another/path/cert.pem ...
> +
> +
> +Constraints
> +===========
> +
> +The following constraints apply when attempting to secure IPL an s390 guest:
> +
> +- z16 CPU model
> +- certificates must be in X.509 PEM format
> +- only support for SCSI scheme of virtio-blk/virtio-scsi devices
> +- a boot device must be specified
> +- any unsupported devices (e.g., ECKD and VFIO) or non-eligible devices (e.g.,
> +  Net) will cause the entire boot process terminating early with an error
> +  logged to the console.
> +
> +
> +Secure IPL Quickstart
> +=====================
> +
> +Build QEMU with gnutls enabled
> +-------------------------------
> +
> +.. code-block:: shell
> +
> +    ./configure … --enable-gnutls
> +
> +Generate certificate (e.g. via certtool)
> +----------------------------------------
> +
> +A private key is required before generating a certificate. This key must be kept secure
> +and confidential.

Please try to keep line length below 80 columns. Longer lines are ok if it 
makes code more readable (or maybe necessary, as in "code-block" sections 
later in this patch), but that's not the case here. See also "Line width" in 
docs/devel/style.rst.

> +Use an RSA private key for signing.
> +
> +.. code-block:: shell
> +
> +    certtool --generate-privkey > key.pem
> +
> +A self-signed certificate requires the organization name. Use the ``cert.info`` template
> +to pre-fill values and avoid interactive prompts from certtool.

dito.

  Thanks,
   Thomas