77 lines
3.4 KiB
Diff
77 lines
3.4 KiB
Diff
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From 38df1fff536527bf47e190d000d8c05679f0f220 Mon Sep 17 00:00:00 2001
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From: Jared Rossi <jrossi@linux.ibm.com>
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Date: Sat, 19 Oct 2024 21:29:52 -0400
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Subject: [PATCH 19/27] docs/system: Update documentation for s390x IPL
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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: 277: Full boot order support for s390x [CentOS 9]
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RH-Jira: RHEL-11424
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RH-Acked-by: Cédric Le Goater <clg@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [19/23] feefab248336e1744eeb6bdf86e9033fe8184b3a (thuth/qemu-kvm-cs9)
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Update docs to show that s390x PC BIOS can support more than one boot device.
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Signed-off-by: Jared Rossi <jrossi@linux.ibm.com>
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Message-ID: <20241020012953.1380075-19-jrossi@linux.ibm.com>
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry picked from commit 0bd107138ff0b171e3cd314dbc200950bcab2b05)
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---
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docs/system/bootindex.rst | 7 ++++---
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docs/system/s390x/bootdevices.rst | 9 ++++++---
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2 files changed, 10 insertions(+), 6 deletions(-)
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diff --git a/docs/system/bootindex.rst b/docs/system/bootindex.rst
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index 8b057f812f..988f7b3beb 100644
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--- a/docs/system/bootindex.rst
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+++ b/docs/system/bootindex.rst
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@@ -49,10 +49,11 @@ Limitations
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-----------
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Some firmware has limitations on which devices can be considered for
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-booting. For instance, the PC BIOS boot specification allows only one
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-disk to be bootable. If boot from disk fails for some reason, the BIOS
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+booting. For instance, the x86 PC BIOS boot specification allows only one
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+disk to be bootable. If boot from disk fails for some reason, the x86 BIOS
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won't retry booting from other disk. It can still try to boot from
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-floppy or net, though.
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+floppy or net, though. In the case of s390x BIOS, the BIOS will try up to
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+8 total devices, any number of which may be disks.
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Sometimes, firmware cannot map the device path QEMU wants firmware to
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boot from to a boot method. It doesn't happen for devices the firmware
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diff --git a/docs/system/s390x/bootdevices.rst b/docs/system/s390x/bootdevices.rst
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index c97efb8fc0..1a1a764c1c 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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@@ -6,9 +6,7 @@ Booting with bootindex parameter
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For classical mainframe guests (i.e. LPAR or z/VM installations), you always
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have to explicitly specify the disk where you want to boot from (or "IPL" from,
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-in s390x-speak -- IPL means "Initial Program Load"). In particular, there can
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-also be only one boot device according to the architecture specification, thus
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-specifying multiple boot devices is not possible (yet).
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+in s390x-speak -- IPL means "Initial Program Load").
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So for booting an s390x guest in QEMU, you should always mark the
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device where you want to boot from with the ``bootindex`` property, for
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@@ -17,6 +15,11 @@ example::
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qemu-system-s390x -drive if=none,id=dr1,file=guest.qcow2 \
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-device virtio-blk,drive=dr1,bootindex=1
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+Multiple devices may have a bootindex. The lowest bootindex is assigned to the
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+device to IPL first. If the IPL fails for the first, the device with the second
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+lowest bootindex will be tried and so on until IPL is successful or there are no
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+remaining boot devices to try.
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+
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For booting from a CD-ROM ISO image (which needs to include El-Torito boot
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information in order to be bootable), it is recommended to specify a ``scsi-cd``
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device, for example like this::
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--
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2.39.3
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