Re: [Qemu-devel] [PATCH v2 4/4] microblaze: boot: Use cpu_set_pc

[Peter Crosthwaite <peter.crosthwaite@xilinx.com>]

On Tue, Jun 16, 2015 at 4:33 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 16 June 2015 at 06:46, Peter Crosthwaite <crosthwaitepeter@gmail.com> wrote:
>> Use cpu_set_pc for setting program counters when bootloading. This
>> removes an instance of system level code having to reach into the CPU
>> env.
>>
>> Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
>> ---
>>  hw/microblaze/boot.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/microblaze/boot.c b/hw/microblaze/boot.c
>> index 4c44317..ec68479 100644
>> --- a/hw/microblaze/boot.c
>> +++ b/hw/microblaze/boot.c
>> @@ -54,7 +54,7 @@ static void main_cpu_reset(void *opaque)
>>      env->regs[5] = boot_info.cmdline;
>>      env->regs[6] = boot_info.initrd_start;
>>      env->regs[7] = boot_info.fdt;
>> -    env->sregs[SR_PC] = boot_info.bootstrap_pc;
>> +    cpu_set_pc(CPU(cpu), boot_info.bootstrap_pc, &error_abort);
>
> Well, it sort of removes an instance of reaching into the CPU
> env, but there's all those other ones in plain sight just above.
> Is there much point in setting SR_PC indirectly if we don't
> have a mechanism for setting the other regs indirectly?
>

Yes. Needs more patches :). I'm starting with the easy stuff, and I am
actually more interested in getting rid of the SR_PC macro usage at
this stage. ARMs solution to this is the machine code bootloader. That
would be one way. But what I want to propose was that we add a virtual
method to CPUs that sets these offsets that bootloaders can call. This
brings us closer to one bootloader that can do it all.

Regards,
Peter

> -- PMM
>