Re: [PATCH 4/5] hw/ppc/ppc4xx_pci: Replace pointless warning by assert()

[Nathan Chancellor <natechancellor@gmail.com>]

On Tue, Sep 01, 2020 at 12:40:42PM +0200, Philippe Mathieu-Daudé wrote:
> We call pci_register_root_bus() to register 4 IRQs with the
> ppc4xx_pci_set_irq() handler. As it can only be called with
> values in the [0-4[ range, replace the pointless warning by
> an assert().
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/ppc/ppc4xx_pci.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/ppc4xx_pci.c b/hw/ppc/ppc4xx_pci.c
> index cd3f192a138..503ef46b39a 100644
> --- a/hw/ppc/ppc4xx_pci.c
> +++ b/hw/ppc/ppc4xx_pci.c
> @@ -256,10 +256,7 @@ static void ppc4xx_pci_set_irq(void *opaque, int irq_num, int level)
>      qemu_irq *pci_irqs = opaque;
>  
>      trace_ppc4xx_pci_set_irq(irq_num);
> -    if (irq_num < 0) {
> -        fprintf(stderr, "%s: PCI irq %d\n", __func__, irq_num);
> -        return;
> -    }
> +    assert(irq_num >= 0);
>      qemu_set_irq(pci_irqs[irq_num], level);
>  }
>  
> -- 
> 2.26.2
> 
> 

Hopefully reporting this here is okay, I find Launchpad hard to use but
I can file it there if need be.

The assertion added by this patch triggers while trying to boot a
ppc44x_defconfig Linux kernel:

$ qemu-system-ppc \
    -machine bamboo \
    -no-reboot \
    -append console=ttyS0 \
    -display none \
    -kernel uImage \
    -m 128m \
    -nodefaults \
    -serial mon:stdio
Linux version 5.11.0-rc3 (nathan@ubuntu-m3-large-x86) (powerpc-linux-gcc (GCC) 10.2.0, GNU ld (GNU Binutils) 2.35) #1 Sun Jan 10 15:52:24 MST 2021
Using PowerPC 44x Platform machine description
ioremap() called early from find_legacy_serial_ports+0x64c/0x794. Use early_ioremap() instead
printk: bootconsole [udbg0] enabled
-----------------------------------------------------
phys_mem_size     = 0x8000000
dcache_bsize      = 0x20
icache_bsize      = 0x20
cpu_features      = 0x0000000000000100
  possible        = 0x0000000040000100
  always          = 0x0000000000000100
cpu_user_features = 0x8c008000 0x00000000
mmu_features      = 0x00000008
-----------------------------------------------------
Zone ranges:
  Normal   [mem 0x0000000000000000-0x0000000007ffffff]
Movable zone start for each node
Early memory node ranges
  node   0: [mem 0x0000000000000000-0x0000000007ffffff]
Initmem setup node 0 [mem 0x0000000000000000-0x0000000007ffffff]
MMU: Allocated 1088 bytes of context maps for 255 contexts
Built 1 zonelists, mobility grouping on.  Total pages: 32448
Kernel command line: console=ttyS0
Dentry cache hash table entries: 16384 (order: 4, 65536 bytes, linear)
Inode-cache hash table entries: 8192 (order: 3, 32768 bytes, linear)
mem auto-init: stack:off, heap alloc:off, heap free:off
Memory: 122712K/131072K available (5040K kernel code, 236K rwdata, 1260K rodata, 200K init, 134K bss, 8360K reserved, 0K cma-reserved)
Kernel virtual memory layout:
  * 0xffbdf000..0xfffff000  : fixmap
  * 0xffbdd000..0xffbdf000  : early ioremap
  * 0xd1000000..0xffbdd000  : vmalloc & ioremap
SLUB: HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
NR_IRQS: 512, nr_irqs: 512, preallocated irqs: 16
UIC0 (32 IRQ sources) at DCR 0xc0
random: get_random_u32 called from start_kernel+0x370/0x508 with crng_init=0
clocksource: timebase: mask: 0xffffffffffffffff max_cycles: 0x5c4093a7d1, max_idle_ns: 440795210635 ns
clocksource: timebase mult[2800000] shift[24] registered
pid_max: default: 32768 minimum: 301
Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
futex hash table entries: 256 (order: -1, 3072 bytes, linear)
NET: Registered protocol family 16
DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations

PCI host bridge /plb/pci@ec000000 (primary) ranges:
 MEM 0x00000000a0000000..0x00000000bfffffff -> 0x00000000a0000000
  IO 0x00000000e8000000..0x00000000e800ffff -> 0x0000000000000000
4xx PCI DMA offset set to 0x00000000
4xx PCI DMA window base to 0x0000000000000000
DMA window size 0x0000000080000000
PCI: Probing PCI hardware
PCI host bridge to bus 0000:00
pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
pci_bus 0000:00: root bus resource [mem 0xa0000000-0xbfffffff]
pci_bus 0000:00: root bus resource [bus 00-ff]
pci_bus 0000:00: busn_res: [bus 00-ff] end is updated to ff
pci 0000:00:00.0: [1014:027f] type 00 class 0x068000
qemu-system-ppc: ../hw/ppc/ppc4xx_pci.c:259: ppc4xx_pci_set_irq: Assertion `irq_num >= 0' failed.

On v5.2.0, it looks like a higher assertion triggers, added by
commit 459ca8bfa4 ("pci: Assert irqnum is between 0 and bus->nirqs in
pci_bus_change_irq_level").

qemu-system-ppc: ../hw/pci/pci.c:253: pci_bus_change_irq_level: Assertion `irq_num >= 0' failed.

I have uploaded the kernel image here:

https://github.com/nathanchance/bug-files/blob/8edf230441bd8eda067973fdf0eb063c94f04379/qemu-0270d74ef886235051c13c39b0de88500c628a02/uImage

Cheers,
Nathan