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qemu-options: Deprecate -old-param command line option

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The '-old-param' command line option is specific to Arm targets; it
is very briefly documented as "old param mode".  What this option
actually does is change the behaviour when directly booting a guest
kernel, so that command line arguments are passed to the kernel using
the extremely old "param_struct" ABI, rather than the newer ATAGS or
even newer DTB mechanisms.

This support was added back in 2007 to support an old vendor kernel
on the akita/terrier board types:
 https://mail.gnu.org/archive/html/qemu-devel/2007-07/msg00344.html
Even then, it was an out-of-date mechanism from the kernel's
point of view -- the kernel has had a comment since 2001 marking
it as deprecated. As of mid-2024, the kernel only retained
param_struct support for the RiscPC and Footbridge platforms:
 https://lore.kernel.org/linux-arm-kernel/2831c5a6-cfbf-4fe0-b51c-0396e5b0aeb7@app.fastmail.com/

None of the board types QEMU supports need param_struct support;
mark this option as deprecated.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-id: 20250127123113.2947620-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2025-02-07 16:09:20 +00:00
parent 76723b8ed7
commit 751002e74a
2 changed files with 14 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

13
docs/about/deprecated.rst
View file

@ -68,6 +68,19 @@ configurations (e.g. -smp drawers=1,books=1,clusters=1 for x86 PC machine) is
marked deprecated since 9.0, users have to ensure that all the topology members
described with -smp are supported by the target machine.
``-old-param`` option for booting Arm kernels via param_struct (since 10.0)
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
The ``-old-param`` command line option is specific to Arm targets:
it is used when directly booting a guest kernel to pass it the
command line and other information via the old ``param_struct`` ABI,
rather than the newer ATAGS or DTB mechanisms. This option was only
ever needed to support ancient kernels on some old board types
like the ``akita`` or ``terrier``; it has been deprecated in the
kernel since 2001. None of the board types QEMU supports need
``param_struct`` support, so this option has been deprecated and will
be removed in a future QEMU version.
User-mode emulator command line arguments
-----------------------------------------

1
system/vl.c
View file

@ -3469,6 +3469,7 @@ void qemu_init(int argc, char **argv)
nb_prom_envs++;
break;
case QEMU_OPTION_old_param:
warn_report("-old-param is deprecated");
old_param = 1;
break;
case QEMU_OPTION_rtc: