Re: [PATCH] docs/system/s390x: Add a chapter about s390x boot devices

[Philippe Mathieu-Daudé]

On 8/10/20 12:18 PM, Cornelia Huck wrote:
> On Thu,  6 Aug 2020 17:05:07 +0200
> Thomas Huth <thuth@redhat.com> wrote:
> 
>> Booting on s390x is a little bit different compared to other architectures.
>> Let's add some information for people who are not yet used to this.
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  docs/system/s390x/bootdevices.rst | 82 +++++++++++++++++++++++++++++++
>>  docs/system/target-s390x.rst      |  1 +
>>  2 files changed, 83 insertions(+)
>>  create mode 100644 docs/system/s390x/bootdevices.rst
>>
>> diff --git a/docs/system/s390x/bootdevices.rst 
>> b/docs/system/s390x/bootdevices.rst
>> new file mode 100644
>> index 0000000000..68f0ffd450
>> --- /dev/null
>> +++ b/docs/system/s390x/bootdevices.rst
>> @@ -0,0 +1,82 @@
>> +Boot devices on s390x
>> +=====================
>> +
>> +Booting with bootindex parameter
>> +--------------------------------
>> +
>> +For classical mainframe guests (i.e. LPAR or z/VM installations), you always
>> +have to exactly specify the disk where you want to boot from (or "IPL" from,
> 
> s/exactly/explictly/ ?

Or "to explicit the disk ..."?

> 
>> +in s390x-speak -- IPL means "Initial Program Load"). Especially, there can
> 
> s/Especially/In particular/ ?
> 
>> +also be only one boot device according to the architecture specification, 
>> thus
>> +specifying multiple boot devices is not possible (yet).
>> +
>> +So for booting an s390x guest in QEMU, you should always mark the
>> +device where you want to boot from with the ``bootindex`` property, for
>> +example::
>> +
>> + qemu-system-s390x -drive if=none,id=dr1,file=guest.qcow2 \
>> +                   -device virtio-blk,drive=dr1,bootindex=1
>> +
>> +For booting from a CD-ROM ISO image (which needs to include El-Torito boot
>> +informatin for being bootable), it is recommended to specify a ``scsi-cd``
> 
> s/informatin for being/information in order to be/
> 
>> +device, for example like this::
>> +
>> + qemu-system-s390x -blockdev file,node-name=c1,filename=... \
>> +                   -device virtio-scsi \
>> +                   -device scsi-cd,drive=c1,bootindex=1
>> +
>> +Note that you really have to use the ``bootindex`` property to select the
>> +boot device. The old-fashioned ``-boot order=...`` command of QEMU (and
>> +also ``-boot once=...``) is not supported on s390x.
> 
> (...)
> 
> This looks good to me, and is certainly helpful. I can fix the nits
> myself and apply it.
> 
> There's also some documentation regarding DASD IPL in the devel guide;
> but as that is mostly helpful for people actually working with the
> code, I don't think that it makes sense to cross-reference it.
> 
>