Am 25.04.20 um 19:32 schrieb Ard Biesheuvel:
On Tue, 21 Apr 2020 at 19:07, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
On Tue, 21 Apr 2020 at 18:43, Christian König <christian.koenig@xxxxxxx> wrote:
Am 21.04.20 um 18:22 schrieb Ard Biesheuvel:
When resizing a BAR, pci_reassign_bridge_resources() is invoked to
bring the bridge windows of parent bridges in line with the new BAR
assignment.
This assumes that the device whose BAR is being resized lives on a
subordinate bus, but this is not necessarily the case. A device may
live on the root bus, in which case dev->bus->self is NULL, and
passing a NULL pci_dev pointer to pci_reassign_bridge_resources()
will cause it to crash.
So let's make the call to pci_reassign_bridge_resources() conditional
on whether dev->bus->self is non-NULL in the first place.
Fixes: 8bb705e3e79d84e7 ("PCI: Add pci_resize_resource() for resizing BARs")
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Sounds like it makes sense, patch is
Reviewed-by: Christian König <christian.koenig@xxxxxxx>.
Thanks Christian.
May I ask where you found that condition?
In this particular case, it was on an ARM board with funky PCIe IP
that does not expose a root port in its bus hierarchy.
But in the general case, PCIe endpoints can be integrated into the
root complex, in which case they appear on the root bus, and there is
no reason such endpoints shouldn't be allowed to have resizable BARs.
Actually, looking at this more carefully, I think
pci_reassign_bridge_resources() needs to do /something/ to ensure that
the resources are reshuffled if needed when the resized BAR overlaps
with another one.
The resized BAR never overlaps with an existing one since to resize a
BAR it needs to be deallocated and disabled. This is done as a
precaution to avoid potential incorrect routing and decode of memory access.
The call to pci_reassign_bridge_resources() is only there to change the
resources of the upstream bridge to the device which is resized and not
to adjust the resources of the device itself.
Regards,
Christian.
Bjorn, did you have any thoughts on this? I could make
pci_reassign_bridge_resources() take a pci_bus, and handle the root
bus as a special case. Alternatively, pci_resize_resource() could make
the distinction, but it will probably need to duplicate some of the
reassignment that goes on in pci_reassign_bridge_resources() as well.
