Re: [Qemu-devel] PowerPC 440 support

[Baojun Wang]

I think the idea is very good, otherwise it will take too much time to
finish, and it gives us a way to lauch kernel directly without a
firmware.

I have some question about the new qemu device tree, in ppc440_bamboo.c:

function bamboo_load_device_tree() is only usable when HAVE_FDT
defined as 1, but currently (even with git version) version (0.10.5)
we can not enable this feature? I have forced HAVE_FDT to be defined
by:

echo '#define HAVE_FDT 1' >> config-host.h

&

echo 'FDT_LIBS=-lfdt' >> config-host.mak

but that lead to compile error, seems device tree in qemu is not fully
populated?

  Regard & Thanks,
Wang

On Mon, Jun 15, 2009 at 11:46 PM, Hollis Blanchard<address@hidden> wrote:
> KVM PPC execution doesn't use firmware today. Instead we create the device
> tree in qemu itself, stuff it into guest memory, and point a guest register
> at it on entry. This was just a shortcut/hack, because we didn't have enough
> time to enable both Linux and uboot.
>
> I agree that the best way to do things long-term is to run u-boot inside the
> guest environment. That will likely require improvements to qemu's device
> emulation, and also we'll probably need to work out a way for qemu to pass
> parameters (e.g. memory size) to u-boot. IMHO, the best approach there would
> be to have u-boot interpret a device tree from qemu, then modify it and pass
> it on to the kernel. Obviously that will require u-boot work.
>
> -Hollis
>
> On Sun, Jun 14, 2009 at 11:40 PM, Baojun Wang <address@hidden> wrote:
>>
>> It seems most boards will converted to the device tree infrastructure?
>>
>> but I think we will need a firmware first before loading the linux
>> kernel, I don't know if qemu-system-ppcemb could run kernel directly
>> without a firmware..
>>
>>  Best Regards,
>> Wang
>>
>> On Mon, Jun 15, 2009 at 3:46 AM, Hollis Blanchard<address@hidden>
>> wrote:
>> > My 440 board is inaccessible for a couple weeks, so I can't test your
>> > patch. That said, the code looks fine.
>> >
>> > However, I wonder what your goal is? You want to be able to create a
>> > Bamboo board with e.g. a 750 processor? I don't think that would help
>> > the original poster, and I'm not sure how useful it is, but I don't
>> > object...
>> >
>> > Either way I guess it will become a non-issue once PowerPC boards are
>> > converted to the device tree infrastructure.
>> >
>> > -Hollis
>> >
>> > On Sun, Jun 14, 2009 at 1:33 PM, Blue Swirl<address@hidden> wrote:
>> >> Sorry, I was very confused (I didn't look at ppc440.c).
>> >>
>> >> For some reason, CPU model can't be specified on the command line. The
>> >> patch allows this, does it look OK?
>> >>
>> >> Is there a kernel and initrd somewhere, so I could test this?
>> >>
>> >> Currently I get (no kernel or ROM, so nothing to execute):
>> >> Truncating memory to 128 MiB to fit SDRAM controller limits.
>> >> ppc405_serial_init: offset 0000000000000300
>> >> QEMU 0.10.50 monitor - type 'help' for more information
>> >> (qemu) qemu: fatal: Trying to execute code outside RAM or ROM at
>> >> 0x00000000fffffffc
>> >>
>> >> NIP 00000000fffffffc   LR 0000000000000000 CTR 0000000000000000 XER
>> >> 00000000
>> >> MSR 0000000000000000 HID0 0000000000000300  HF 0000000000000000 idx 1
>> >> Segmentation fault
>> >>
>> >> On 6/14/09, Hollis Blanchard <address@hidden> wrote:
>> >>> Yes, I wrote the code you quoted.
>> >>>
>> >>>  In case there is any confusion, let me restate: You can boot a Bamboo
>> >>>  (PowerPC 440) guest under KVM on a PowerPC 440 host. KVM bypasses
>> >>>  qemu's CPU emulation (TCG), but uses qemu's device emulation.
>> >>>  Therefore, if someone were to implement 440 core emulation in qemu,
>> >>>  you could boot a 440 kernel with qemu without KVM.
>> >>>
>> >>>  Most devices found on 440 SoCs are the same as or very similar to the
>> >>>  devices found on 405 SoCs. Qemu's 440 device emulation isn't perfect,
>> >>>  but because Linux is highly modular, with a modified device tree you
>> >>>  can boot it. See pc-bios/bamboo.dts.
>> >>>
>> >>>  -Hollis
>> >>>
>> >>>  On Sat, Jun 13, 2009 at 10:47 PM, Baojun Wang <address@hidden>
>> >>> wrote:
>> >>>  >
>> >>>  > in hw/ppc440.c:
>> >>>  >
>> >>>  >    env = cpu_ppc_init("440EP");
>> >>>  >    if (!env && kvm_enabled()) {
>> >>>  >        /* XXX Since qemu doesn't yet emulate 440, we just say it's
>> >>> a 405.
>> >>>  >         * Since KVM doesn't use qemu's CPU emulation it seems to be
>> >>> working
>> >>>  >         * OK. */
>> >>>  >        env = cpu_ppc_init("405");
>> >>>  >    }
>> >>>  >    if (!env) {
>> >>>  >        fprintf(stderr, "Unable to initialize CPU!\n");
>> >>>  >        exit(1);
>> >>>  >    }
>> >>>  >
>> >>>  > also in hw/ppc.c:
>> >>>  >
>> >>>  > I can find ppc40x_irq_init/e500_irq_init(used mpc8544ds), but there
>> >>> is
>> >>>  > no ppcbooke_irq_init? It seems hw/ppc405_uc.c is emulation for
>> >>> DCRs,
>> >>>  > PLB, DMA, GPIO, I2C.., but there is no hw/ppc44x_uc.c.
>> >>>  >
>> >>>  > the qemu source I used is 0.10.5.
>> >>>  >
>> >>>  > Also in ppc/translate_init.c, there lots of CONFIG_USER_ONLY, but I
>> >>>  > many of them are DEBUG or CACHE related SPR emulation, and since
>> >>> qemu
>> >>>  > doesn't emulate cache, I think it's OK.
>> >>>  >
>> >>>  >  Thanks,
>> >>>  > Wang
>> >>>  >
>> >>>  > On Sun, Jun 14, 2009 at 1:47 AM, Hollis
>> >>> Blanchard<address@hidden> wrote:
>> >>>  > > On Fri, Jun 12, 2009 at 10:48 AM, Blue Swirl
>> >>> <address@hidden> wrote:
>> >>>  > >>
>> >>>  > >> On 6/11/09, Baojun Wang <address@hidden> wrote:
>> >>>  > >> > could qemu emulate some board like bamboo (without kvm) or
>> >>> MPC8544ds
>> >>>  > >> > now? Thanks
>> >>>  > >>
>> >>>  > >> Yes, if someone adds emulation for these devices: UIC, PLB, DMA,
>> >>> POB,
>> >>>  > >> EBC, IIC, ZMII. Maybe some are not needed in all cases.
>> >>>  > >
>> >>>  > > No, qemu still doesn't emulate Book E cores, such as the PowerPC
>> >>> 440 in a
>> >>>  > > Bamboo board.
>> >>>  > >
>> >>>  > > UIC is of course emulated, otherwise KVM guests on 440 wouldn't
>> >>> get very
>> >>>  > > far. :) Enough 440 SoC devices are emulated to support Linux boot
>> >>> with a
>> >>>  > > properly stripped device tree.
>> >>>  > >
>> >>>  > > -Hollis
>> >>>  > >
>> >>>
>> >>
>> >
>
>