Re: [Qemu-devel] [PATCH 2/6] A cumulative MIPS patchset

[Thiemo Seufer]

Stefan Weil wrote:
> Hello Thiemo,
> 
> my reboot patch for MIPS
> (http://lists.gnu.org/archive/html/qemu-devel/2006-09/msg00082.html)
> is only partially included in Daniel's patch.
> 
> As far as I know, a MIPS triggers the reboot exception at power-on.
> (at least for MIPS 4KEc), so my patch uses the same code for reboot
> exception and power-on.

Actually, a MIPS has no notion of "reboot". Is starts up by executing
from the reset vector at 0xbfc00000, which is the place where the
firmware ROM resides. A "soft reset" exception could be used to signal
reboot, but that is then handled by software, and system specific.

> Why do we need a special QEMU reset device in the Linux kernel?
> QEMU might emulate existing real reset devices as well...

Because we want to have both reboot and halt for linux, and ATM
we have no firmware in Qemu to handle that.

Given the number of incompatible MIPS firmwares out there it might
be a bad idea to rely on any of those, unless we improve the Qemu
emulation to resemble a real system with its respective firmware.


Thiemo