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71 lines
3.0 KiB
71 lines
3.0 KiB
From 407e23d7f0c9020404247afe7d4df98505222bbb Mon Sep 17 00:00:00 2001
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From: Thomas Huth <thuth@redhat.com>
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Date: Mon, 14 Nov 2022 14:25:02 +0100
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Subject: [PATCH 1/3] docs/system/s390x: Document the "loadparm" machine
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property
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Thomas Huth <thuth@redhat.com>
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RH-MergeRequest: 233: s390x: Document the "loadparm" machine property
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RH-Bugzilla: 2128225
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: Cédric Le Goater <clg@redhat.com>
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RH-Acked-by: Jon Maloy <jmaloy@redhat.com>
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RH-Commit: [1/2] e9589ea32d2a8f82971476b644e1063fa14cf822
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The "loadparm" machine property is useful for selecting alternative
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kernels on the disk of the guest, but so far we do not tell the users
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yet how to use it. Add some documentation to fill this gap.
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Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=2128235
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Message-Id: <20221114132502.110213-1-thuth@redhat.com>
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Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry picked from commit be5df2edb5d69ff3107c5616aa035a9ba8d0422e)
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---
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docs/system/s390x/bootdevices.rst | 26 ++++++++++++++++++++++++++
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1 file changed, 26 insertions(+)
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diff --git a/docs/system/s390x/bootdevices.rst b/docs/system/s390x/bootdevices.rst
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index 9e591cb9dc..d4bf3b9f0b 100644
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--- a/docs/system/s390x/bootdevices.rst
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+++ b/docs/system/s390x/bootdevices.rst
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@@ -53,6 +53,32 @@ recommended to specify a CD-ROM device via ``-device scsi-cd`` (as mentioned
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above) instead.
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+Selecting kernels with the ``loadparm`` property
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+------------------------------------------------
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+
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+The ``s390-ccw-virtio`` machine supports the so-called ``loadparm`` parameter
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+which can be used to select the kernel on the disk of the guest that the
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+s390-ccw bios should boot. When starting QEMU, it can be specified like this::
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+
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+ qemu-system-s390x -machine s390-ccw-virtio,loadparm=<string>
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+
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+The first way to use this parameter is to use the word ``PROMPT`` as the
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+``<string>`` here. In that case the s390-ccw bios will show a list of
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+installed kernels on the disk of the guest and ask the user to enter a number
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+to chose which kernel should be booted -- similar to what can be achieved by
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+specifying the ``-boot menu=on`` option when starting QEMU. Note that the menu
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+list will only show the names of the installed kernels when using a DASD-like
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+disk image with 4k byte sectors. On normal SCSI-style disks with 512-byte
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+sectors, there is not enough space for the zipl loader on the disk to store
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+the kernel names, so you only get a list without names here.
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+
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+The second way to use this parameter is to use a number in the range from 0
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+to 31. The numbers that can be used here correspond to the numbers that are
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+shown when using the ``PROMPT`` option, and the s390-ccw bios will then try
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+to automatically boot the kernel that is associated with the given number.
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+Note that ``0`` can be used to boot the default entry.
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+
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+
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Booting from a network device
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-----------------------------
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--
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2.37.3
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