From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AB8JxZoK++TPLPkLvyiveabwJJzwvzVeK8JDTzrCFtJF6jX5U5HTZUvur/7CAfoT/3u+n6J5E51l ARC-Seal: i=1; a=rsa-sha256; t=1525958112; cv=none; d=google.com; s=arc-20160816; b=XVcH2+PIoFWkoif7g4yn//UJNuQKrSyiZsmDM4pT8ezfLJ1ak/+C7MEbwgYwQGyEx+ fJzfuZIivSBRwOU87SUwNzeDM5m9C8e8Nf0+xQ47JoCCPRGW1Z8jf8cR9m906dPm3i2J XYF7UsipIH9aWrdbEoHmY7O5LcWNI2RMQQ1TMP3bSkj3LdjL1QGeaH/GaxpcPyR/HgXZ 3cCRMDeDCFbh9WDhLDD2x0xDkJ/1wjQ3eqhXfLByciV3gVLVReWZvTg5Y4D/d4Je6nT2 +SA8yVuNtqxZg1U3r5P16Iltqjdv5A6WkjV/s5aQZWeAmGp8N/3eAYO3q0vR/5O7XeO8 Gx1g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:message-id:references:in-reply-to:subject:cc:to:from :date:content-transfer-encoding:mime-version:dkim-signature :dkim-signature:arc-authentication-results; bh=d5Y/ZWF56vMci3YItllxLFgFjw1yWqhzSE4Pn1xDR4I=; b=dDXWD5tc8b2d8pyFTEUMMQRjg03j1tby2bHh/zp/FKl+2d+w2z1JOKVHCIGsfKazGc 366Eo87qMTozmr+mLsOCgALWFtn3EXpN8ga0E5toqO3ySX2ta1lFbZf5otTn3+e8K4W3 uVg+NRG/do8/YByZNiNEBnRRb2+fEN7Ln0FdW13en43asdqsPyXI41eQf/kFgr3iwUEZ PwRESm614/8CuzQqabQjPeXVKk49bzzrPJnlMhFuD0SAdpX+IUYHHuxwzY/585iAi96E AdBihRX+UxQ0jJx9wOblL5P6ktnWS3ZIHoDOkyF6Jf1D8KBg+CkK0D08pLoZk6AWnan+ TGYw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@codeaurora.org header.s=default header.b=a+bLjevH; dkim=pass header.i=@codeaurora.org header.s=default header.b=bL9M5gMD; spf=pass (google.com: domain of okaya@codeaurora.org designates 198.145.29.96 as permitted sender) smtp.mailfrom=okaya@codeaurora.org Authentication-Results: mx.google.com; dkim=pass header.i=@codeaurora.org header.s=default header.b=a+bLjevH; dkim=pass header.i=@codeaurora.org header.s=default header.b=bL9M5gMD; spf=pass (google.com: domain of okaya@codeaurora.org designates 198.145.29.96 as permitted sender) smtp.mailfrom=okaya@codeaurora.org MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 10 May 2018 14:15:10 +0100 From: okaya@codeaurora.org To: Bjorn Helgaas Cc: poza@codeaurora.org, Bjorn Helgaas , Philippe Ombredanne , Thomas Gleixner , Greg Kroah-Hartman , Kate Stewart , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Dongdong Liu , Keith Busch , Wei Zhang , Timur Tabi , linux-pci-owner@vger.kernel.org Subject: Re: [PATCH v15 3/9] PCI/AER: Handle ERR_FATAL with removal and re-enumeration of devices In-Reply-To: <20180510131027.GB173327@bhelgaas-glaptop.roam.corp.google.com> References: <1525323838-1735-1-git-send-email-poza@codeaurora.org> <1525323838-1735-4-git-send-email-poza@codeaurora.org> <20180508235330.GN161390@bhelgaas-glaptop.roam.corp.google.com> <20180509130730.GA236548@bhelgaas-glaptop.roam.corp.google.com> <20180509232111.GA43216@bhelgaas-glaptop.roam.corp.google.com> <20180510131027.GB173327@bhelgaas-glaptop.roam.corp.google.com> Message-ID: <3cb8c2046967fd9a81a8f846dbafaa82@codeaurora.org> User-Agent: Roundcube Webmail/1.2.5 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1599417977501212020?= X-GMAIL-MSGID: =?utf-8?q?1600083053498947091?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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 >> > > > > > >> > > > > > 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? >> 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. >> >>