Re: virtio-pci in qemu-system-arm is broken in 8.2

[Peter Maydell]

On Thu, 4 Jan 2024 at 17:17, Michael Tokarev <mjt@tls.msk.ru> wrote:
>
> 04.01.2024 19:25, Michael Tokarev wrote:
> ...
> > this archive contains kernel+initrd.  I run it this way:
> >
> > qemu-system-arm -append root=LABEL=debvm -nographic -machine type=virt \
> >   -drive media=disk,format=raw,file=vmlinuz,if=virtio,snapshot=on \
> >   -no-user-config -m 1G -kernel vmlinuz -initrd initrd.img
>
> This is actually even more fishy.
>
> The reproducer needs -cpu max to "work." Without -cpu max, it
> fails to recognize virtio pci devices in both cases - in 8.2.0
> with or without the commit in question (b8f7959f28c4f36496).
> Only with -cpu max it works after reverting b8f7959f28c.
>
> Additional kernel message in case when it doesn't work:
>
> [    1.372841] pci-host-generic 4010000000.pcie: \
>    can't claim ECAM area [mem 0x10000000-0x1fffffff]: \
>    address conflict with pcie@10000000 [mem 0x10000000-0x3efeffff]
>
> which isn't generated in case everything's ok.

I'm trying to figure out what kind of kernel config causes
this. If I do an upstream build of v6.6.9 with this config:
https://people.linaro.org/~peter.maydell/arm-6.6.9-config

then it successfully probes the PCI device even with -cpu max:

pci-host-generic 4010000000.pcie: host bridge /pcie@10000000 ranges:
pci-host-generic 4010000000.pcie:       IO 0x003eff0000..0x003effffff
-> 0x0000000000
pci-host-generic 4010000000.pcie:      MEM 0x0010000000..0x003efeffff
-> 0x0010000000
pci-host-generic 4010000000.pcie:      MEM 0x8000000000..0xffffffffff
-> 0x8000000000
pci-host-generic 4010000000.pcie: Memory resource size exceeds max for 32 bits
pci-host-generic 4010000000.pcie: ECAM at [mem
0x4010000000-0x401fffffff] for [bus 00-ff]
pci-host-generic 4010000000.pcie: PCI host bridge to bus 0000:00

So what's different about your kernel and config that
causes the pci controller not to probe?

thanks
-- PMM