On Thu, Apr 12, 2018 at 08:39:54AM -0600, Keith Busch wrote: > On Thu, Apr 12, 2018 at 10:34:37AM -0400, Sinan Kaya wrote: > > On 4/12/2018 10:06 AM, Bjorn Helgaas wrote: > > > > > > I think the scenario you are describing is two systems that are > > > identical except that in the first, the endpoint is below a hotplug > > > bridge, while in the second, it's below a non-hotplug bridge. There's > > > no physical hotplug (no drive removed or inserted), and DPC is > > > triggered in both systems. > > > > > > I suggest that DPC should be handled identically in both systems: > > > > > > - The PCI core should have the same view of the endpoint: it should > > > be removed and re-added in both cases (or in neither case). > > > > > > - The endpoint itself should not be able to tell the difference: it > > > should see a link down event, followed by a link retrain, followed > > > by the same sequence of config accesses, etc. > > > > > > - The endpoint driver should not be able to tell the difference, > > > i.e., we should be calling the same pci_error_handlers callbacks > > > in both cases. > > > > > > It's true that in the non-hotplug system, pciehp probably won't start > > > re-enumeration, so we might need an alternate path to trigger that. > > > > > > But that's not what we're doing in this patch. In this patch we're > > > adding a much bigger difference: for hotplug bridges, we stop and > > > remove the hierarchy below the bridge; for non-hotplug bridges, we do > > > the AER-style flow of calling pci_error_handlers callbacks. > > > > Our approach on V12 was to go to AER style recovery for all DPC events > > regardless of hotplug support or not. > > > > Keith was not comfortable with this approach. That's why, we special cased > > hotplug. > > > > If we drop 6/6 on this patch on v13, we achieve this. We still have to > > take care of Keith's inputs on individual patches. > > > > we have been struggling with the direction for a while. > > > > Keith, what do you think? > > My only concern was for existing production environments that use DPC > for handling surprise removal, and I don't wish to break the existing > uses. Also, I thought the plan was to keep hotplug and non-hotplug the same, except for the very end: if not a hotplug bridge, initiate the rescan automatically after releasing from containment, otherwise let pciehp handle it when the link reactivates.
