On 2019-04-18 10:33 a.m., Bjorn Helgaas wrote:
On Thu, Apr 18, 2019 at 01:58:59PM +0200, Christian König wrote:
A lot of root complexes can still do P2P even when PCI devices
don't share a common upstream bridge.
Start adding a whitelist and allow P2P if both participants are
attached to known good root complex.
Is there a plan for addressing this in a generic way that doesn't
require an OS modification for every new "known good root complex",
e.g., some PCIe or ACPI spec update that allows the OS to discover
this?
I'm aware of work going on in the PCI SIG to address this [1].
But I expect it's going to be a long time before actual hardware
advertises this capability to indicate support. So in the interim we
either need to not use p2pdma on root complexes or create a white list.
I'm in favour of the white list approach.
Logan
[1] https://lore.kernel.org/linux-pci/20181210115653.0000615a@xxxxxxxxxx/
