Currently we allocate IO BARs bottom-up in the
EfiPciHostBridgeAllocateResources phase of the enumeration.
> GCD:AddIoSpace(Base=0000000000000000,Length=0000000000010000)
> GcdIoType = I/O
> Status = Success
> GCDIoType Range
> ========== =================================
> I/O 0000000000000000-000000000000FFFF
Because the IO aperture is based at zero, the first allocation happens to
get the zero address. However, a zero address for a PCI BAR is considered
unmapped; see eg.:
- <http://www.pcisig.com/reflector/msg00459.html>,
- the (new_addr == 0) part in QEMU, pci_bar_address() [hw/pci/pci.c]:
new_addr = pci_get_long(d->config + bar) & ~(size - 1);
last_addr = new_addr + size - 1;
/* Check if 32 bit BAR wraps around explicitly.
* TODO: make priorities correct and remove this work around.
*/
if (last_addr <= new_addr || new_addr == 0 || last_addr >= UINT32_MAX)
{
return PCI_BAR_UNMAPPED;
}
We can avoid this problem by allocating top-down in the IO aperture.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Olivier Martin <Olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16905 6f19259b-4bc3-4df7-8a09-765794883524
ef8dba7da3