Bug in qemu-system-ppc running fedora 12 ppc guest

[Howard Spoelstra <hsp.cat7@gmail.com>]

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Hi,

Qemu-system-ppc built from current master can no longer run Fedora 12 ppc
as guest. (This the only ppc distro I tested.) Host is Fedora 34. Please
see screen shot attached.
Booting from both an installation DVD and from an installed system fail.

To reproduce:
compile qemu-system-ppc from current master and run:

./qemu-system-ppc \
-M mac99,via=pmu \
-m 1024 \
-L pc-bios \
-boot d \
-cdrom Fedora-12-ppc-DVD.iso \
-g 1024x768x8

I tracked the issue down to this commit:

8f0a4b6a9b40e18116a2bb6bbcc00feb8119c792 is the first bad commit
commit 8f0a4b6a9b40e18116a2bb6bbcc00feb8119c792
Author: Matheus Ferst <matheus.ferst@eldorado.org.br>
Date:   Tue Jun 1 16:35:28 2021 -0300

    target/ppc: Move cmp/cmpi/cmpl/cmpli to decodetree

    Additionally, REQUIRE_64BIT when L=1 to match what is specified in The
    Programming Environments Manual:

    "For 32-bit implementations, the L field must be cleared, otherwise the
    instruction form is invalid."

    Some CPUs are known to deviate from this specification by ignoring the
    L bit [1]. The stricter behavior, however, can help users that test
    software with qemu, making it more likely to detect bugs that would
    otherwise be silent.

    If deemed necessary, a future patch can adapt this behavior based on
    the specific CPU model.

    [1] The 601 manual is the only one I've found that explicitly states
    that the L bit is ignored, but we also observe this behavior in a 7447A
    v1.2.

    Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
    Message-Id: <20210601193528.2533031-15-matheus.ferst@eldorado.org.br>
    Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
    [dwg: Corrected whitespace error]
    Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

 target/ppc/insn32.decode                   | 14 ++++++++
 target/ppc/translate.c                     | 52
------------------------------
 target/ppc/translate/fixedpoint-impl.c.inc | 31 ++++++++++++++++++
 3 files changed, 45 insertions(+), 52 deletions(-)

Best,
Howard

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