[Qemu-ppc] ppc: regression in 2.7.0-rc3 on rfi/rfid/hrfi instructions

[Hervé Poussineau]

Hi,

Following patch regresses Linux boot on PReP machine:

commit a2e71b28e832346409efc795ecd1f0a2bcb705a3
Author: Benjamin Herrenschmidt <address@hidden>
Date:   Tue Jun 21 23:48:46 2016 +0200

    ppc: Fix rfi/rfid/hrfi/... emulation

    This reworks emulation of the various "rfi" variants. I removed
    some masking bits that I couldn't make sense of, the only bit that
    I am aware we should mask here is POW, the CPU's MSR mask should
    take care of the rest.

    This also fixes some problems when running 32-bit userspace under
    a 64-bit kernel.

    This patch broke 32bit OpenBIOS when run under a 970 cpu. A fix was
    proposed here :

        https://www.coreboot.org/pipermail/openbios/2016-June/009452.html

    Signed-off-by: Benjamin Herrenschmidt <address@hidden>
    Reviewed-by: David Gibson <address@hidden>
    [clg: updated the commit log with the reference of the openbios fix ]
    Signed-off-by: Cédric Le Goater <address@hidden>
    [dwg: Remove hunk which disabled rfi on 64-bit CPUS.  The change was
     correct, but we need to fix OpenBIOS before applying it]
    Signed-off-by: David Gibson <address@hidden>

Test case:
- Download: http://www.juneau-lug.org/zImage.initrd.sandalfoot
- Run: qemu-system-ppc -M prep -kernel zImage.initrd.sandalfoot

Firmware starts, loads kernel, but seems to error out just after PS/2 detection.

Reverting the commit and fixing the conflict makes it work again, up to shell.

Hervé