Yes, it is a CPU feature, and yes you can select the exception vector prefix with the MSR[IP] bit which should be set by a hardware reset. The initial value seems wrong in qemu but that seems to fixed by the machine-specific initialization. The 'none' machine, however, just uses generic code and does not do anything PPC-specific. This means that
- the MSR and probably other registers, too, are not initialized to what the hardware documentation specifies as reset values. - the time-base is not initialized at all (and this leads to a segfault when you start the ppc 'none' machine) - probably other things are not properly initialized. I wonder, e.g., about the MMU... It seems that all registers are simply initialized to zero. Then, there seems to be a 'reset' function which initializes the registers to the proper reset values (well - sort of bug 812398 reports that HID0 is not properly initialized by some CPU flavours). However, that reset function is not executed by the 'none' machine initialization.... -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/811683 Title: 7400,7410,7450 cpus vector have wrong exception prefix at reset Status in QEMU: Triaged Bug description: I have a proprietary ROM implementing system calls that are executed via the 'SC' instruction. I use qemu-0.14.1, qemu-system-ppc -M prep -cpu $CPU -bios my_bios -kernel my_kernel That works fine on a 604 (CPU=0x00040103) - but does not on an emulated 7400 (CPU=0x000c0209) or 7450 (CPU=0x80000201). I found that the emulator jumps to 0x00000c00 instead of 0xfff00c00. Probably this is due to a wrong setting in target-ppc/translate_init.c: init_excp_604() correctly sets env->hreset_vector=0xfff00000UL; but init_excp_7400() says env->hreset_vector=0x00000000UL; which seems wrong. (the 7400 manual says a hard-reset jumps initializes the prefix to 0xfff00000.) Likewise, init_excp_7450() (and probably other, related CPUs) are wrong. Indeed, when I change the value in init_excp_7400() to 0xfff00000UL then everything works as expected for me. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/811683/+subscriptions
