Hi Bjorn, Was away briefly for the holidays, comments below: > On Nov 24, 2020, at 9:17 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > 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: That’s ultimately what we are trying to do. > > 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). In the past recall we were augmenting it with bridge = dev->rcec for RC_END. But we were able to relocate the handling in aer_root_reset(). So in this patch - we add the conditionals because RC_END is being passed in addition to RC_EC. 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); So we need to check for RP, DS, and RC_EC @@ -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); + } Breaking out a separate patch would be unnecessary as you correctly point out that it’s only going to be an RP or DS before this patch. Thanks, Sean >>>> + } >>>> pci_info(bridge, "device recovery successful\n"); >>>> return status; >>>> >>>> -- >>>> 2.29.2 >>
