Re: Is the ppc440 "bamboo" board in QEMU still of any use?

[Christophe Leroy]

Le 14/10/2021 à 11:31, Thomas Huth a écrit :
>   Hi,
>
> I tried to build a current Linux kernel for the "bamboo" board and use 
> it in QEMU, but QEMU then quickly aborts with:
>
>   pci.c:262: pci_bus_change_irq_level: Assertion `irq_num >= 0' failed.
>
> (or with a "DCR write error" if I try to use the cuImage instead).
>
> I googled a little bit and found this discussion:
>
> https://qemu-devel.nongnu.narkive.com/vYHona3u/emulating-powerpc-440ep-with-qemu-system-ppcemb#post2 
>
>
> Seems like this board was used for KVM on the PPC440 only, and has never 
> been enabled with the TCG emulation?
>
> Well, KVM support on the 440 has been removed years ago already:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b2677b8dd8de0dc1496ede4da09b9dfd59f15cea 
>
>
> So is this "bamboo" board dead code in QEMU now? Or does anybody still 
> have a kernel binary which could be used for testing it? Note: This 
> board does not support "-bios", so u-boot or other firmwares are 
> certainly also not an option here...
> Should we mark "bamboo" as deprecated nowadays?

I have the following change in QEMU to be able to run the bamboo, found 
it some time ago via google (can't remember where):

diff --git a/hw/ppc/ppc4xx_pci.c b/hw/ppc/ppc4xx_pci.c
index 8147ba6f94..600e89e791 100644
--- a/hw/ppc/ppc4xx_pci.c
+++ b/hw/ppc/ppc4xx_pci.c
@@ -246,7 +246,7 @@ static int ppc4xx_pci_map_irq(PCIDevice *pci_dev, 
int irq_num)

     trace_ppc4xx_pci_map_irq(pci_dev->devfn, irq_num, slot);

-    return slot - 1;
+    return slot ? slot - 1 : slot;
 }

 static void ppc4xx_pci_set_irq(void *opaque, int irq_num, int level)
---

It's probably no the final change, but at least it allows booting bamboo 
on qemu again.

Christophe