Messages in this thread | | | Date | Thu, 10 May 2018 19:48:48 +0530 | From | poza@codeauro ... | Subject | Re: [PATCH v15 3/9] PCI/AER: Handle ERR_FATAL with removal and re-enumeration of devices |
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On 2018-05-10 18:45, okaya@codeaurora.org wrote: > On 2018-05-10 14:10, Bjorn Helgaas wrote: >> On Thu, May 10, 2018 at 12:31:16PM +0530, poza@codeaurora.org wrote: >>> On 2018-05-10 04:51, Bjorn Helgaas wrote: >>> > On Wed, May 09, 2018 at 06:44:53PM +0530, poza@codeaurora.org wrote: >>> > > On 2018-05-09 18:37, Bjorn Helgaas wrote: >>> > > > On Tue, May 08, 2018 at 06:53:30PM -0500, Bjorn Helgaas wrote: >>> > > > > On Thu, May 03, 2018 at 01:03:52AM -0400, Oza Pawandeep wrote: >>> > > > > > This patch alters the behavior of handling of ERR_FATAL, where removal >>> > > > > > of devices is initiated, followed by reset link, followed by >>> > > > > > re-enumeration. >>> > > > > > >>> > > > > > So the errors are handled in a different way as follows: >>> > > > > > ERR_NONFATAL => call driver recovery entry points >>> > > > > > ERR_FATAL => remove and re-enumerate >>> > > > > > >>> > > > > > please refer to Documentation/PCI/pci-error-recovery.txt for more details. >>> > > > > > >>> > > > > > Signed-off-by: Oza Pawandeep <poza@codeaurora.org> >>> > > > > > >>> > > > > > diff --git a/drivers/pci/pcie/aer/aerdrv.c b/drivers/pci/pcie/aer/aerdrv.c >>> > > > > > index 779b387..206f590 100644 >>> > > > > > --- a/drivers/pci/pcie/aer/aerdrv.c >>> > > > > > +++ b/drivers/pci/pcie/aer/aerdrv.c >>> > > > > > @@ -330,6 +330,13 @@ static pci_ers_result_t aer_root_reset(struct pci_dev *dev) >>> > > > > > reg32 |= ROOT_PORT_INTR_ON_MESG_MASK; >>> > > > > > pci_write_config_dword(dev, pos + PCI_ERR_ROOT_COMMAND, reg32); >>> > > > > > >>> > > > > > + /* >>> > > > > > + * This function is called only on ERR_FATAL now, and since >>> > > > > > + * the pci_report_resume is called only in ERR_NONFATAL case, >>> > > > > > + * the clearing part has to be taken care here. >>> > > > > > + */ >>> > > > > > + aer_error_resume(dev); >>> > > > > >>> > > > > I don't understand this part. Previously the ERR_FATAL path looked >>> > > > > like >>> > > > > this: >>> > > > > >>> > > > > do_recovery >>> > > > > reset_link >>> > > > > driver->reset_link >>> > > > > aer_root_reset >>> > > > > pci_reset_bridge_secondary_bus # <-- reset >>> > > > > broadcast_error_message(..., report_resume) >>> > > > > pci_walk_bus(..., report_resume, ...) >>> > > > > report_resume >>> > > > > if (cb == report_resume) >>> > > > > pci_cleanup_aer_uncorrect_error_status >>> > > > > pci_write_config_dword(PCI_ERR_UNCOR_STATUS) # <-- clear >>> > > > > status >>> > > > > >>> > > > > After this patch, it will look like this: >>> > > > > >>> > > > > do_recovery >>> > > > > do_fatal_recovery >>> > > > > pci_cleanup_aer_uncorrect_error_status >>> > > > > pci_write_config_dword(PCI_ERR_UNCOR_STATUS) # <-- clear >>> > > > > status >>> > > > > reset_link >>> > > > > driver->reset_link >>> > > > > aer_root_reset >>> > > > > pci_reset_bridge_secondary_bus # <-- reset >>> > > > > aer_error_resume >>> > > > > pcie_capability_write_word(PCI_EXP_DEVSTA) # >>> > > > > <-- clear more >>> > > > > pci_write_config_dword(PCI_ERR_UNCOR_STATUS) # >>> > > > > <-- clear status >>> > > > > >>> > > > > So if I'm understanding correctly, the new path clears the status too >>> > > > > early, then clears it again (plus clearing DEVSTA, which we didn't do >>> > > > > before) later. >>> > > > > >>> > > > > I would think we would want to leave aer_root_reset() alone, and >>> > > > > just move >>> > > > > the pci_cleanup_aer_uncorrect_error_status() in do_fatal_recovery() >>> > > > > down so >>> > > > > it happens after we call reset_link(). That way the reset/clear >>> > > > > sequence >>> > > > > would be the same as it was before. >>> > > > >>> > > > I've been fiddling with this a bit myself and will post the results to >>> > > > see >>> > > > what you think. >>> > > >>> > > >>> > > ok so you are suggesting to move >>> > > pci_cleanup_aer_uncorrect_error_status down >>> > > which I can do. >>> > > >>> > > And not to call aer_error_resume, because you think its clearing the >>> > > status >>> > > again. >>> > > >>> > > following code: calls aer_error_resume. >>> > > pci_broadcast_error_message() >>> > > /* >>> > > * If the error is reported by an end point, we >>> > > think this >>> > > * error is related to the upstream link of the end >>> > > point. >>> > > */ >>> > > if (state == pci_channel_io_normal) >>> > > /* >>> > > * the error is non fatal so the bus is ok, >>> > > just >>> > > invoke >>> > > * the callback for the function that logged >>> > > the >>> > > error. >>> > > */ >>> > > cb(dev, &result_data); >>> > > else >>> > > pci_walk_bus(dev->bus, cb, &result_data); >>> > >>> > Holy crap, I thought this could not possibly get any more complicated, >>> > but you're right; we do actually call aer_error_resume() today via an >>> > extremely convoluted path: >>> > >>> > do_recovery(pci_dev) >>> > broadcast_error_message(..., error_detected, ...) >>> > if (AER_FATAL) >>> > reset_link(pci_dev) >>> > udev = BRIDGE ? pci_dev : pci_dev->bus->self >>> > driver->reset_link(udev) >>> > aer_root_reset(udev) >>> > if (CAN_RECOVER) >>> > broadcast_error_message(..., mmio_enabled, ...) >>> > if (NEED_RESET) >>> > broadcast_error_message(..., slot_reset, ...) >>> > broadcast_error_message(dev, ..., report_resume, ...) >>> > if (BRIDGE) >>> > report_resume >>> > driver->resume >>> > pcie_portdrv_err_resume >>> > device_for_each_child(..., resume_iter) >>> > resume_iter >>> > driver->error_resume >>> > aer_error_resume >>> > pci_cleanup_aer_uncorrect_error_status(pci_dev) # only if >>> > BRIDGE >>> > pci_write_config_dword(PCI_ERR_UNCOR_STATUS) >>> > >>> > aerdriver is the only port service driver that implements >>> > .error_resume(), and aerdriver only binds to root ports. I can't >>> > really believe all these device_for_each_child()/resume_iter() >>> > gyrations are necessary when this is AER code calling AER code. >>> > >>> > Bjorn >>> >>> here is the code of do_fatal_recovery, where I have moved the things >>> down >>> and doing only if it is bridge. >>> let me know how this looks to you, so then I can post v16. >> >> This looks superficially OK. It is very difficult for me to verify >> that >> the behavior is equivalent to the current code, but that's not your >> fault; >> it's just a consequence of the existing design. >> >> I have a couple trivial comments elsewhere, and I'll respond to those >> patches individually. >> >>> static pci_ers_result_t do_fatal_recovery(struct pci_dev *dev, int >>> severity) >>> { >>> struct pci_dev *udev; >>> struct pci_bus *parent; >>> struct pci_dev *pdev, *temp; >>> struct aer_broadcast_data result_data; >>> pci_ers_result_t result = PCI_ERS_RESULT_RECOVERED; >>> >>> >>> if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) >>> udev = dev; >>> else >>> udev = dev->bus->self; >>> >>> parent = udev->subordinate; >>> pci_lock_rescan_remove(); >>> list_for_each_entry_safe_reverse(pdev, temp, >>> &parent->devices, >>> bus_list) { >>> pci_dev_get(pdev); >>> pci_dev_set_disconnected(pdev, NULL); >>> if (pci_has_subordinate(pdev)) >>> pci_walk_bus(pdev->subordinate, >>> pci_dev_set_disconnected, NULL); >>> pci_stop_and_remove_bus_device(pdev); >>> pci_dev_put(pdev); >>> } >>> >>> result = reset_link(udev, severity); >>> if (severity == AER_FATAL && dev->hdr_type == >>> PCI_HEADER_TYPE_BRIDGE) { >>> pci_walk_bus(dev->subordinate, report_resume, >>> &result_data); > > Why are we calling resume?
the reason we have to call resume here, because we are not calling aer_resume() any more in root_reset. and we have to call resume only in bridge case. please have a look at couple of conversation back with Bjorn. the objective is to align the sequence close to the current code.
> >>> pci_cleanup_aer_uncorrect_error_status(dev); >>> dev->error_state = pci_channel_io_normal; >>> } >>> if (result == PCI_ERS_RESULT_RECOVERED) >>> if (pcie_wait_for_link(udev, true)) >>> pci_rescan_bus(udev->bus); >>> >>> pci_unlock_rescan_remove(); >>> >>> return result; >>> } >>> >>> Regards, >>> Oza. >>> >>>
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