Re: [Qemu-devel] MIPS64 problem with ethernet

[Jason Wessel <jason.wessel@windriver.com>]

Aurelien Jarno wrote:
> As discussed on IRC, the problem is only present on 32-bit hosts. It is
> due to the do_ddivu which is falsely implemented using lldiv and then by
> casting the result. The patch below uses / and % as on the 64-bit host
> code. It is maybe slower than lldiv, but at least it gives the correct
> result. This probably involves some libgcc code, so it is better to keep
> it in op_helper.c for 32-bit hosts.
>
>   

With your change the ethernet does come up but it seems there is a 
further problem, perhaps with ddivu.  My host is a 32bit host, and this 
does seem to work on a 64bit host or the real hardware.  Doing something 
like an ls /proc does not work in the emulated target.   The reason is 
that the compatibility syscalls are 32bit and there is some sign 
extension problem somewhere.

I put the following code in kernel/main/init.c as an illustration of the 
problem.
    {
        unsigned long v1 = 0xffffffff80731111;
        unsigned int v2 = v1 + 1;
        printk("v1 %lx v2 %08x\n", v1, v2);
    }

On the real hw it prints correctly as:
v1 ffffffff80731111 v2 80731112

On the emulated 64 bit + 64bit kernel on a 32 bit host it prints as:
v1 ffffffff80731111 v2 ffffffff80731112

This might be due to the ddivu in printk, but it could be elsewhere...

Jason.