On Thu, Apr 18, 2019 at 10:58:55AM -0600, Logan Gunthorpe wrote: > 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. I agree we need a whitelist; I just want to make sure we also make progress on some way to limit the amount of time we need to update it. > [1] https://lore.kernel.org/linux-pci/20181210115653.0000615a@xxxxxxxxxx/
