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From: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Date: Fri, 14 Jun 2013 15:49:21 +0530
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Subject: [Qemu-devel] commit 08521e2 breaks SLOF usb boot
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To: qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, qemu-ppc@nongnu.org, Alexander Graf <agraf@suse.de>


Hi,

I have a working usb echi storage support for SLOF. I found that with
latest qemu HEAD, USB EHCI registers(HCSPARAMS) started appearing funnily
- in place of being LE it appeared BE. Bisecting it down I could get to
this zero to the following commit:


commit 08521e28c7e6e8cc1f53424a0f845f58d2ed9546
Author: Paolo Bonzini <pbonzini@redhat.com>
Date:   Fri May 24 12:54:01 2013 +0200

    memory: add big endian support to access_with_adjusted_size
    
    This will be used to split 8-byte access down to two four-byte accesses.
    
    Reviewed-by: Richard Henderson <rth@twiddle.net>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>


If I hack the above funniness in my USB EHCI driver, somewhere down the
qemu crashes at code introduced by this patch:

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0 0x0000000000000000 in ?? ()
#1 0x00005555557a0ea4 in access_with_adjusted_size (addr=addr@entry=12, value=value@entry=0x7fffd5a86680, size=size@entry=1, access_size_min=<optimized out>, access_size_max=<optimized out>,
access=0x5555557a1f80 <memory_region_oldmmio_write_accessor>, opaque=0x5555567f8ab8) at /home/nikunj/work/power/code/qemu/memory.c:396
#2 0x00005555557a5ebb in memory_region_dispatch_write (size=1, data=0, addr=12, mr=0x5555567f8ab8) at /home/nikunj/work/power/code/qemu/memory.c:998

Reverting this, I can safely boot using a usb-storage device put on ehci controller.

Regards
Nikunj