[22.04 FEAT] KVM: Allow long kernel command lines for QEMU

[bugproxy]

KVM: Allow long kernel command lines for QEMU

Description:
Originally, the kernel command line length was limited to 896 bytes, due to its fixed size in the kernel image. Recent kernels can support larger command lines by checking out the position and length using new fields in the kernel image. This feature allows QEMU direct kernel boot to use larger command lines.

[Frank Heimes (fheimes)]

Changing to Incomplete for now, until kernel version and/or commits are shared for integration.

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2022-02-04 08:17 EDT-------
There are only changes in QEMU and the commit is b2173046a64b ("s390x/ipl: support extended kernel command line size"). Of course, to make use of this feature the guest kernel has to support extended kernel cmdline sizes.

[Frank Heimes (fheimes)]

Updating the affected component from kernel to qemu.

[Frank Heimes (fheimes)]

But the kernelsupport for long command lines is not in place yet for jammy.
I think it's kernel commit "s390: support command lines longer than 896 bytes" 5ecb2da660ab,
and that went upstream with 5.16, hence it's not in jammy's 5.15 master-next yet (I just double checked).
Hence I'm adding here again kernel as affected component.

[Frank Heimes (fheimes)]

Unfortunately, "s390: support command lines longer than 896 bytes" 5ecb2da660ab does not apply while tying to cherry pick, hence a backport for kernel 5.15 is needed.

[Christian Ehrhardt  (paelzer)]

Thanks for the report, since this isn't in a released qemu version so far I've added it to the qemu 6.2 that I'm preparing right now.

[bugproxy (bugproxy)]

------- Comment From <email address hidden> 2022-02-08 07:17 EDT-------
FWIW: Backporting the long kernel command line is not a pre-req for adding this to QEMU. This change is required to support *guests* which have the necessary kernel support(e.g. future Ubuntu 22.10 or upcoming HWE kernels).

[Frank Heimes (fheimes)]

@Viktor, yes sure - and Christian already started to get it in (#7).
But since jammy is an LTS I think it would just make sense to have the kernel patch in 5.15 as well.

[Frank Heimes (fheimes)]

So just for the records:
with first picking:
277c8389386e ("390/kexec_file: move kernel image size check")
before
5ecb2da660ab ("s390: support command lines longer than 896 bytes")
I get the code into jammy's master-next.

[Christian Ehrhardt  (paelzer)]

FYI: If you want/need a test - builds of the qemu that have that are in https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/4753

[Frank Heimes (fheimes)]

Since a separate ticket got opened for the kernel part here: LP#1960580
I'm removing the 'affects kernel' portion from this one.

[Launchpad Janitor (janitor)]

This bug was fixed in the package qemu - 1:6.2+dfsg-2ubuntu5

---------------
qemu (1:6.2+dfsg-2ubuntu5) jammy; urgency=medium

  * d/p/u/tcg-Remove-dh_alias-indirection-for-dh_typecode.patch: fix 32bit
    tcg on s390x.

qemu (1:6.2+dfsg-2ubuntu4) jammy; urgency=medium

  * No-change rebuild to update maintainer scripts, see LP: 1959054

qemu (1:6.2+dfsg-2ubuntu3) jammy; urgency=medium

  * Merge with Debian unstable, remaining changes:
    - qemu-kvm to systemd unit
      - d/qemu-kvm-init: script for QEMU KVM preparation modules, ksm,
        hugepages and architecture specifics
      - d/qemu-system-common.qemu-kvm.service: systemd unit to call
        qemu-kvm-init
      - d/qemu-system-common.install: install helper script
      - d/qemu-system-common.qemu-kvm.default: defaults for
        /etc/default/qemu-kvm
      - d/rules: call dh_installinit and dh_installsystemd for qemu-kvm
    - Distribution specific machine type
      (LP: 1304107 1621042 1776189 1761372 1761372 1776189)
      - d/p/ubuntu/define-ubuntu-machine-types.patch: define distro machine
        types containing release versioned machine attributes
      - d/qemu-system-x86.NEWS Info on fixed machine type defintions
        for host-phys-bits=true
      - Add an info about -hpb machine type in debian/qemu-system-x86.NEWS
      - ubuntu-q35 alias added to auto-select the most recent q35 ubuntu type
    - Enable nesting by default
      - d/p/ubuntu/enable-svm-by-default.patch: Enable nested svm by default
        in qemu64 on amd
        [ No more strictly needed, but required for backward compatibility ]
    - tolerate ipxe size change on migrations to >=18.04 (LP: 1713490)
      - d/p/ubuntu/pre-bionic-256k-ipxe-efi-roms.patch: old machine types
        reference 256k path
      - d/control-in: depend on ipxe-qemu-256k-compat-efi-roms to be able to
        handle incoming migrations from former releases.
    - d/qemu-system-x86.README.Debian: add info about updated nesting changes
    - d/p/lp-1952448-relax-skiboot-gcc-deprecation-errors.patch:
      add patch to workaround FTBFS when building against OpenSSL 3.0.
    - d/optionrom.mak, d/p/u/avoid-fcf-clashing-with-i486.patch: fix
      -fcf-protection being unavailble on -march=i486 (LP 1940029)
    - Ease the use of module retention on upgrades (LP 1913421)
      - debian/qemu-block-extra.postinst: enable mount unit on install/upgrade
    - Make qemu-system-x86-microvm a transitional package as the binary is now
      in qemu-system-x86 itself.
  * Dropped Changes [now part of 1:6.1+dfsg-8]:
    - updated debian/patches/linux-user-binfmt-P.diff to work with in-kernel code
      (#993658) (LP 1947860)
    - improved dependencies
      - Make qemu-system-common depend on qemu-block-extra
      - Make qemu-utils depend on qemu-block-extra
    - d/control*, d/rules: disable xen by default, but provide universe
      package qemu-system-x86-xen as alternative
      [includes compat links changes of 5.0-5ubuntu4]
    - d/p/ubuntu/lp-1929926-*: avoid segfaults by uretprobes (LP 1929926)
  * Dropped Changes [now part of upstream]
    - d/p/u/lp-1932175-s390x-cpumodel-add-3931-and-3932.patch: add new 3931
      and 3932 mac...