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From: Blue Swirl <blauwirbel@gmail.com>
Date: Sun, 7 Nov 2010 14:56:03 +0000
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Subject: [Qemu-devel] Re: [sparc] Unassigned mem read access on writing?
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To: Artyom Tarasenko <atar4qemu@gmail.com>
Cc: qemu-devel <qemu-devel@nongnu.org>

On Fri, Nov 5, 2010 at 5:48 PM, Artyom Tarasenko <atar4qemu@gmail.com> wrot=
e:
> Trying to boot Solaris 2.1 I get the following error message:
>
> Unassigned mem read access of 1 byte to ffffffffffff0768 from f0014768
> qemu: fatal: Trap 0x29 while interrupts disabled, Error state
> pc: f0014768 =C2=A0npc: f001476c
>
> Looks like a read access to a non-mapped memory (the NF-bit is 0). But
> where can it happen?
>
> The code:
>
> =C2=A0 0xf001475c: =C2=A0mov =C2=A00x200, %o4
> =3D> 0xf0014760: =C2=A0lda =C2=A0[ %o4 ] #ASI_N, %o3
> =C2=A0 0xf0014764: =C2=A0sta =C2=A0%o2, [ %o4 ] #ASI_N
> =C2=A0 0xf0014768: =C2=A0sta =C2=A0%g0, [ %o0 ] (3)
> =C2=A0 0xf001476c: =C2=A0cmp =C2=A0%o2, %o3
> =C2=A0 0xf0014770: =C2=A0bne =C2=A00xf001477c
> End of assembler dump.
> (gdb) stepi
> 0xf0014764 in ?? ()
> (gdb) info registers o2
> o2 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 0x28a =C2=A0 =C2=A0650
> (gdb) stepi
> Remote connection closed
> (gdb)
>
> Any ideas how to debug?

All accesses are 32 bits wide. ASI_N is 4 and the other store access
is to ASI 3 (MMU flush). I don't see how this is possible.

Perhaps PC and NPC are not updated as they should. If you insert a
breakpoint at the offending instruction, do you get the same error as
above with the same PC/NPC value?