Messages in this thread | | | Subject | Re: [PATCH] PCI: ERR: Don't override the status returned by error_detect() | From | "Kuppuswamy, Sathyanarayanan" <> | Date | Thu, 28 May 2020 21:24:43 -0700 |
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On 5/28/20 9:04 PM, Z.q. Hou wrote: > Hi Kuppuswamy, > >> -----Original Message----- >> From: Kuppuswamy, Sathyanarayanan >> <sathyanarayanan.kuppuswamy@linux.intel.com> >> Sent: 2020年5月29日 5:19 >> To: Z.q. Hou <zhiqiang.hou@nxp.com>; linux-pci@vger.kernel.org; >> linux-kernel@vger.kernel.org; ruscur@russell.cc; sbobroff@linux.ibm.com; >> oohall@gmail.com; bhelgaas@google.com >> Subject: Re: [PATCH] PCI: ERR: Don't override the status returned by >> error_detect() >> >> Hi, >> >> On 5/27/20 1:31 AM, Zhiqiang Hou wrote: >>> From: Hou Zhiqiang <Zhiqiang.Hou@nxp.com> >>> >>> The commit 6d2c89441571 ("PCI/ERR: Update error status after >>> reset_link()") overrode the 'status' returned by the error_detect() >>> call back function, which is depended on by the next step. This >>> overriding makes the Endpoint driver's required info (kept in the var >>> status) lost, so it results in the fatal errors' recovery failed and then kernel >> panic. >> Can you explain why updating status affects the recovery ? > > Take the e1000e as an example: > Once a fatal error is reported by e1000e, the e1000e's error_detect() will be > called and it will return PCI_ERS_RESULT_NEED_RESET to request a slot reset, > the return value is stored in the '&status' of the calling > pci_walk_bus(bus,report_frozen_detected, &status). > If you update the 'status' with the reset_link()'s return value > (PCI_ERS_RESULT_RECOVERED if the reset link succeed), then the 'status' has > the value PCI_ERS_RESULT_RECOVERED and e1000e's request > PCI_ERS_RESULT_NEED_RESET lost, then e1000e's callback function .slot_reset() > will be skipped and directly call the .resume(). I believe you are working with non hotplug capable device. If yes, then this issue will be addressed by the following patch. https://lkml.org/lkml/2020/5/6/1545 > > So this is how the update of 'status' break the handshake between RC's AER driver > and the Endpoint's protocol driver error_handlers, then result in the recovery failure. > >>> >>> In the e1000e case, the error logs: >>> pcieport 0002:00:00.0: AER: Uncorrected (Fatal) error received: >>> 0002:01:00.0 e1000e 0002:01:00.0: AER: PCIe Bus Error: >>> severity=Uncorrected (Fatal), type=Inaccessible, (Unregistered Agent >>> ID) pcieport 0002:00:00.0: AER: Root Port link has been reset >> As per above commit log, it looks like link is reset correctly. > > Yes, see my comments above. > > Thanks, > Zhiqiang > >>> SError Interrupt on CPU0, code 0xbf000002 -- SError >>> CPU: 0 PID: 111 Comm: irq/76-aerdrv Not tainted >>> 5.7.0-rc7-next-20200526 #8 Hardware name: LS1046A RDB Board (DT) >>> pstate: 80000005 (Nzcv daif -PAN -UAO BTYPE=--) pc : >>> __pci_enable_msix_range+0x4c8/0x5b8 >>> lr : __pci_enable_msix_range+0x480/0x5b8 >>> sp : ffff80001116bb30 >>> x29: ffff80001116bb30 x28: 0000000000000003 >>> x27: 0000000000000003 x26: 0000000000000000 >>> x25: ffff00097243e0a8 x24: 0000000000000001 >>> x23: ffff00097243e2d8 x22: 0000000000000000 >>> x21: 0000000000000003 x20: ffff00095bd46080 >>> x19: ffff00097243e000 x18: ffffffffffffffff >>> x17: 0000000000000000 x16: 0000000000000000 >>> x15: ffffb958fa0e9948 x14: ffff00095bd46303 >>> x13: ffff00095bd46302 x12: 0000000000000038 >>> x11: 0000000000000040 x10: ffffb958fa101e68 >>> x9 : ffffb958fa101e60 x8 : 0000000000000908 >>> x7 : 0000000000000908 x6 : ffff800011600000 >>> x5 : ffff00095bd46800 x4 : ffff00096e7f6080 >>> x3 : 0000000000000000 x2 : 0000000000000000 >>> x1 : 0000000000000000 x0 : 0000000000000000 Kernel panic - not >>> syncing: Asynchronous SError Interrupt >>> CPU: 0 PID: 111 Comm: irq/76-aerdrv Not tainted >>> 5.7.0-rc7-next-20200526 #8 >>> >>> I think it's the expected result that "if the initial value of error >>> status is PCI_ERS_RESULT_DISCONNECT or >> PCI_ERS_RESULT_NO_AER_DRIVER >>> then even after successful recovery (using reset_link()) >>> pcie_do_recovery() will report the recovery result as failure" which >>> is described in commit 6d2c89441571 ("PCI/ERR: Update error status after >> reset_link()"). >>> >>> Refer to the Documentation/PCI/pci-error-recovery.rst. >>> As the error_detect() is mandatory callback if the pci_err_handlers is >>> implemented, if it return the PCI_ERS_RESULT_DISCONNECT, it means the >>> driver doesn't want to recover at all; For the case >>> PCI_ERS_RESULT_NO_AER_DRIVER, if the pci_err_handlers is not >>> implemented, the failure is more expected. >>> >>> Fixes: commit 6d2c89441571 ("PCI/ERR: Update error status after >>> reset_link()") >>> Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com> >>> --- >>> drivers/pci/pcie/err.c | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> >>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c index >>> 14bb8f54723e..84f72342259c 100644 >>> --- a/drivers/pci/pcie/err.c >>> +++ b/drivers/pci/pcie/err.c >>> @@ -165,8 +165,7 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev >> *dev, >>> pci_dbg(dev, "broadcast error_detected message\n"); >>> if (state == pci_channel_io_frozen) { >>> pci_walk_bus(bus, report_frozen_detected, &status); >>> - status = reset_link(dev); >>> - if (status != PCI_ERS_RESULT_RECOVERED) { >>> + if (reset_link(dev) != PCI_ERS_RESULT_RECOVERED) { >>> pci_warn(dev, "link reset failed\n"); >>> goto failed; >>> } >>> >> >> -- >> Sathyanarayanan Kuppuswamy >> Linux Kernel Developer
-- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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