On Mon, Nov 23, 2020 at 11:57:35PM +0000, Kelley, Sean V wrote: > > On Nov 23, 2020, at 3:28 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Fri, Nov 20, 2020 at 04:10:31PM -0800, Sean V Kelley wrote: > >> In some cases a bridge may not exist as the hardware controlling may be > >> handled only by firmware and so is not visible to the OS. This scenario is > >> also possible in future use cases involving non-native use of RCECs by > >> firmware. > >> > >> Explicitly apply conditional logic around these resets by limiting them to > >> Root Ports and Downstream Ports. > > > > Can you help me understand this? The subject says "Limit AER resets" > > and here you say "limit them to RPs and DPs", but it's not completely > > obvious how the resets are being limited, i.e., the patch doesn't add > > anything like: > > > > + if (type == PCI_EXP_TYPE_ROOT_PORT || > > + type == PCI_EXP_TYPE_DOWNSTREAM) > > reset_subordinates(bridge); > > > > It *does* add checks around pcie_clear_device_status(), but that also > > includes RC_EC. And that's not a reset, so I don't think that's > > explicitly mentioned in the commit log. > > The subject should have referred to the clearing of the device status rather than resets. > It originally came from this simpler patch in which I made use of reset instead of clear: > > https://lore.kernel.org/linux-pci/20201002184735.1229220-8-seanvk.dev@xxxxxxxxxxxxxxxx/ > > So a rephrase of clearing in place of resets would be more appropriate. > > Then we added the notion of bridges…below > > > > > Also see the question below. > > > >> Link: https://lore.kernel.org/r/20201002184735.1229220-8-seanvk.dev@xxxxxxxxxxxxxxxx > >> Signed-off-by: Sean V Kelley <sean.v.kelley@xxxxxxxxx> > >> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > >> Acked-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> > >> --- > >> drivers/pci/pcie/err.c | 31 +++++++++++++++++++++++++------ > >> 1 file changed, 25 insertions(+), 6 deletions(-) > >> > >> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c > >> index 8b53aecdb43d..7883c9791562 100644 > >> --- a/drivers/pci/pcie/err.c > >> +++ b/drivers/pci/pcie/err.c > >> @@ -148,13 +148,17 @@ static int report_resume(struct pci_dev *dev, void *data) > >> > >> /** > >> * pci_walk_bridge - walk bridges potentially AER affected > >> - * @bridge: bridge which may be a Port > >> + * @bridge: bridge which may be a Port, an RCEC with associated RCiEPs, > >> + * or an RCiEP associated with an RCEC > >> * @cb: callback to be called for each device found > >> * @userdata: arbitrary pointer to be passed to callback > >> * > >> * If the device provided is a bridge, walk the subordinate bus, including > >> * any bridged devices on buses under this bus. Call the provided callback > >> * on each device found. > >> + * > >> + * If the device provided has no subordinate bus, call the callback on the > >> + * device itself. > >> */ > >> static void pci_walk_bridge(struct pci_dev *bridge, > >> int (*cb)(struct pci_dev *, void *), > >> @@ -162,6 +166,8 @@ static void pci_walk_bridge(struct pci_dev *bridge, > >> { > >> if (bridge->subordinate) > >> pci_walk_bus(bridge->subordinate, cb, userdata); > >> + else > >> + cb(bridge, userdata); > >> } > >> > >> pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> @@ -174,10 +180,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> > >> /* > >> * Error recovery runs on all subordinates of the bridge. If the > >> - * bridge detected the error, it is cleared at the end. > >> + * bridge detected the error, it is cleared at the end. For RCiEPs > >> + * we should reset just the RCiEP itself. > >> */ > >> if (type == PCI_EXP_TYPE_ROOT_PORT || > >> - type == PCI_EXP_TYPE_DOWNSTREAM) > >> + type == PCI_EXP_TYPE_DOWNSTREAM || > >> + type == PCI_EXP_TYPE_RC_EC || > >> + type == PCI_EXP_TYPE_RC_END) > >> bridge = dev; > >> else > >> bridge = pci_upstream_bridge(dev); > >> @@ -185,6 +194,12 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> pci_dbg(bridge, "broadcast error_detected message\n"); > >> if (state == pci_channel_io_frozen) { > >> pci_walk_bridge(bridge, report_frozen_detected, &status); > >> + if (type == PCI_EXP_TYPE_RC_END) { > >> + pci_warn(dev, "subordinate device reset not possible for RCiEP\n"); > >> + status = PCI_ERS_RESULT_NONE; > >> + goto failed; > >> + } > >> + > >> status = reset_subordinates(bridge); > >> if (status != PCI_ERS_RESULT_RECOVERED) { > >> pci_warn(bridge, "subordinate device reset failed\n"); > >> @@ -217,9 +232,13 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev, > >> pci_dbg(bridge, "broadcast resume message\n"); > >> pci_walk_bridge(bridge, report_resume, &status); > >> > >> - if (pcie_aer_is_native(bridge)) > >> - pcie_clear_device_status(bridge); > >> - pci_aer_clear_nonfatal_status(bridge); > >> + if (type == PCI_EXP_TYPE_ROOT_PORT || > >> + type == PCI_EXP_TYPE_DOWNSTREAM || > >> + type == PCI_EXP_TYPE_RC_EC) { > >> + if (pcie_aer_is_native(bridge)) > >> + pcie_clear_device_status(bridge); > >> + pci_aer_clear_nonfatal_status(bridge); > > > > This is hard to understand because "type" is from "dev", but "bridge" > > is not necessarily the same device. Should it be this? > > > > type = pci_pcie_type(bridge); > > if (type == PCI_EXP_TYPE_ROOT_PORT || > > ...) > > Correct, it would be better if the type was based on the ‘bridge’. OK. This is similar to https://lore.kernel.org/linux-pci/20201002184735.1229220-8-seanvk.dev@xxxxxxxxxxxxxxxx/, which you cited above except for the bridge/dev question and the addition here of RC_EC. I tried to split that back into its own patch and started with the commit message from that patch. But I got stuck on the commit message. I got as far as: In some cases an error may be reported by a device not visible to the OS, e.g., if firmware manages the device and passes error information to the OS via ACPI APEI. But I still can't quite connect that to the patch. "bridge" is clearly a device visible to Linux. I guess we're trying to assert that if "bridge" is not a Root Port, Downstream Port, or RCEC, we shouldn't clear the error status because the error came from a device Linux doesn't know about. But I think "bridge" is *always* either a Root Port or a Downstream Port: if (type == PCI_EXP_TYPE_ROOT_PORT || type == PCI_EXP_TYPE_DOWNSTREAM) bridge = dev; else bridge = pci_upstream_bridge(dev); pci_upstream_bridge() returns either NULL (in which case previous uses dereference a NULL pointer), or dev->bus->self, which is always a Root Port, Switch Downstream Port, or Switch Upstream Port (or NULL for the special case of VFs). > >> + } > >> pci_info(bridge, "device recovery successful\n"); > >> return status; > >> > >> -- > >> 2.29.2 >
