[Qemu-devel] Infinite recursion in pci_default_read_config()

[Hannes Reinecke]

Hi all,

when using PCI device-assignment I ran into a nice infinite recursion with 
pci_default_read_config:

uint32_t pci_default_read_config(PCIDevice *d,
                                 uint32_t address, int len)
{
    uint32_t val = 0;
    assert(len == 1 || len == 2 || len == 4);

    if (pci_access_cap_config(d, address, len)) {
        return d->cap.config_read(d, address, len);
    }

    len = MIN(len, pci_config_size(d) - address);
    memcpy(&val, d->config + address, len);
    return le32_to_cpu(val);
}

and d->cap.config_read points to:

(gdb) print *d
$3 = {qdev = {id = 0xc99b10 "01:10.0", state = DEV_STATE_INITIALIZED, 
    opts = 0xc99ad0, hotplugged = 0, info = 0x837e60, parent_bus = 0xc71710, 
    num_gpio_out = 0, gpio_out = 0x0, num_gpio_in = 0, gpio_in = 0x0, 
    child_bus = {lh_first = 0x0}, num_child_bus = 0, sibling = {
      le_next = 0xc99c30, le_prev = 0xc71730}}, 
  config = 0xca3010 "\206\200\312\020\003", 
  cmask = 0xca3120 "\377\377\377\377", wmask = 0xca3230 "", 
  used = 0xca3340 "", bus = 0xc71710, devfn = 32, 
  name = "pci-assign", '\000' <repeats 53 times>, io_regions = {{
      addr = 4060102656, size = 16384, filtered_size = 16384, type = 0 '\000', 
      map_func = 0x46a5f0 <assigned_dev_iomem_map>}, {addr = 0, size = 0, 
      filtered_size = 0, type = 0 '\000', map_func = 0}, {addr = 0, size = 0, 
      filtered_size = 0, type = 0 '\000', map_func = 0}, {addr = 4060119040, 
      size = 16384, filtered_size = 16384, type = 0 '\000', 
      map_func = 0x46a5f0 <assigned_dev_iomem_map>}, {addr = 0, size = 0, 
      filtered_size = 0, type = 0 '\000', map_func = 0}, {addr = 0, size = 0, 
      filtered_size = 0, type = 0 '\000', map_func = 0}, {addr = 0, size = 0, 
      filtered_size = 0, type = 0 '\000', map_func = 0}}, 
  config_read = 0x46a050 <assigned_dev_pci_read_config>, 
  config_write = 0x469f30 <assigned_dev_pci_write_config>, irq = 0xca3450, 
  irq_state = 0 '\000', cap_present = 0, msix_cap = 0 '\000', 
  msix_entries_nr = 0, msix_table_page = 0x0, msix_mmio_index = 0, 
  msix_entry_used = 0x0, msix_bar_size = 0, version_id = 2, 
  msix_page_size = 0, msix_irq_entries = 0x0, cap = {supported = 1, 
    start = 64, length = 16, 
    config_read = 0x416770 <pci_default_cap_read_config>, 
    config_write = 0x46b750 <assigned_device_pci_cap_write_config>}}

which is:

uint32_t pci_default_cap_read_config(PCIDevice *pci_dev,
                                     uint32_t address, int len)
{
    return pci_default_read_config(pci_dev, address, len);
}

Surprisingly, after 100 iterations qemu segfaulted ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                   zSeries & Storage
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SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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