On 04/21/2016 08:07 AM, Sylvain Garrigues wrote:
Le 21 avr. 2016 à 15:42, Peter Maydell <peter.mayd...@linaro.org> a écrit :
There may be something we can do here to make FreeBSD's life
easier, but we definitely can't do it on the eve of a release.
I didn’t know it was release day, my timing is not perfect then, sorry about
that, I didn’t intend to put stress on you guys today.
Like you mentioned, the Linux boot protocol doesn’t mandate any loading
address, hence the possibility to set it on the command line.
It would benefit not only to FreeBSD (which is strictly Linux boot ABI
compliant BTW - that is how I found the qemu bootloader bug and fixed it in
b4850e5) but all other OS.
On the real hardware Raspberry Pi, there is the kernel_address firmware feature
which enable to set the kernel load address. Would be neat to have it *someday*
in qemu for any board if it is not too hard to implement.
It would indeed be nice if qemu for the Pi implemented the exact same
bootloader setup as real HW does. That is, loading boot images from the
FAT partition on the SD card, parsing config.txt, etc.
Ideally as was mentioned earlier this would be done by simply executing
the existing bootloader under emulation, rather than building all that
code into qemu. However, in the Pi case, the bootloader runs on the
VideoCore (a separate non-ARM CPU), so isn't (and likely won't be since
IIUC it isn't fully documented) emulated by qemu. by the time the ARM
CPU runs, everything (kernel, DTB/ATAGS, ARM boot stub, ...) is already
loaded into RAM, the display is already probed over HDMI and the
controller scanning out a dummy image, etc.
So I think if that were to be supported, it'd have to be coded into
qemu. Is that something that could happen, or would such patches not fit
qemu's model well?
