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Message-ID: <20260128150243.000012d8@huawei.com>
Date: Wed, 28 Jan 2026 15:02:43 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Shuai Xue <xueshuai@...ux.alibaba.com>
CC: <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linuxppc-dev@...ts.ozlabs.org>, <bhelgaas@...gle.com>, <kbusch@...nel.org>,
<sathyanarayanan.kuppuswamy@...ux.intel.com>, <mahesh@...ux.ibm.com>,
<oohall@...il.com>, <terry.bowman@....com>, <tianruidong@...ux.alibaba.com>,
<lukas@...ner.de>
Subject: Re: [PATCH v7 2/5] PCI/DPC: Run recovery on device that detected
the error
On Wed, 28 Jan 2026 20:27:31 +0800
Shuai Xue <xueshuai@...ux.alibaba.com> wrote:
> On 1/27/26 6:24 PM, Jonathan Cameron wrote:
> > On Sat, 24 Jan 2026 15:45:54 +0800
> > Shuai Xue <xueshuai@...ux.alibaba.com> wrote:
> >
> >> The current implementation of pcie_do_recovery() assumes that the
> >> recovery process is executed for the device that detected the error.
> >> However, the DPC driver currently passes the error port that experienced
> >> the DPC event to pcie_do_recovery().
> >>
> >> Use the SOURCE ID register to correctly identify the device that
> >> detected the error. When passing the error device, the
> >> pcie_do_recovery() will find the upstream bridge and walk bridges
> >> potentially AER affected. And subsequent commits will be able to
> >> accurately access AER status of the error device.
> >>
> >> Should not observe any functional changes.
> >>
> >> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> >> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
Hi Shuai,
> >> ---
> >> drivers/pci/pci.h | 2 +-
> >> drivers/pci/pcie/dpc.c | 25 +++++++++++++++++++++----
> >> drivers/pci/pcie/edr.c | 7 ++++---
> >> 3 files changed, 26 insertions(+), 8 deletions(-)
> >>
...
> >> -void dpc_process_error(struct pci_dev *pdev)
> >> +/**
> >> + * dpc_process_error - handle the DPC error status
> >> + * @pdev: the port that experienced the containment event
> >> + *
> >> + * Return: the device that detected the error.
> >> + *
> >> + * NOTE: The device reference count is increased, the caller must decrement
> >> + * the reference count by calling pci_dev_put().
> >> + */
> >> +struct pci_dev *dpc_process_error(struct pci_dev *pdev)
> >
> > Maybe it makes sense to carry the err_port naming for the pci_dev
> > in here as well? Seems stronger than just relying on people
> > reading the documentation you've added.
>
> Good point. I think renaming the parameter would improve clarity. However,
> I'd prefer to handle it in a separate patch to keep this change focused on
> the functional modification. Would that work for you?
>
Sure. Ideal would be a precursor patch, but if it's much easier to
do on top of this I'm fine with that.
You are absolutely correct that it should be a separate patch!
> >
> >> {
> >> u16 cap = pdev->dpc_cap, status, source, reason, ext_reason;
> >> struct aer_err_info info = {};
> >> + struct pci_dev *err_dev;
> >>
> >> pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status);
> >>
> >> @@ -279,6 +289,7 @@ void dpc_process_error(struct pci_dev *pdev)
> >> pci_aer_clear_nonfatal_status(pdev);
> >> pci_aer_clear_fatal_status(pdev);
> >> }
> >> + err_dev = pci_dev_get(pdev);
> >> break;
> >> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_NFE:
> >> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE:
> >> @@ -290,6 +301,8 @@ void dpc_process_error(struct pci_dev *pdev)
> >> "ERR_FATAL" : "ERR_NONFATAL",
> >> pci_domain_nr(pdev->bus), PCI_BUS_NUM(source),
> >> PCI_SLOT(source), PCI_FUNC(source));
> >> + err_dev = pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
> >> + PCI_BUS_NUM(source), source & 0xff);
> >
> > Bunch of replication in her with the pci_warn(). Maybe some local variables?
> > Maybe even rebuild the final parameter from PCI_DEVFN(slot, func) just to make the
> > association with the print really obvious?
>
> Agreed. Here's the improved version:
>
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -293,17 +293,28 @@ struct pci_dev *dpc_process_error(struct pci_dev *pdev)
> break;
> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_NFE:
> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE:
> - pci_read_config_word(pdev, cap + PCI_EXP_DPC_SOURCE_ID,
> - &source);
> + {
> + int domain, bus;
> + u8 slot, func, devfn;
> + const char *err_type;
> +
> + pci_read_config_word(pdev, cap + PCI_EXP_DPC_SOURCE_ID, &source);
> +
> + /* Extract source device location */
> + domain = pci_domain_nr(pdev->bus);
> + bus = PCI_BUS_NUM(source);
> + slot = PCI_SLOT(source);
> + func = PCI_FUNC(source);
> + devfn = PCI_DEVFN(slot, func);
> +
> + err_type = (reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE) ?
> + "ERR_FATAL" : "ERR_NONFATAL";
> +
> pci_warn(pdev, "containment event, status:%#06x, %s received from %04x:%02x:%02x.%d\n",
> - status,
> - (reason == PCI_EXP_DPC_STATUS_TRIGGER_RSN_FE) ?
> - "ERR_FATAL" : "ERR_NONFATAL",
> - pci_domain_nr(pdev->bus), PCI_BUS_NUM(source),
> - PCI_SLOT(source), PCI_FUNC(source));
> - err_dev = pci_get_domain_bus_and_slot(pci_domain_nr(pdev->bus),
> - PCI_BUS_NUM(source), source & 0xff);
> + status, err_type, domain, bus, slot, func);
> + err_dev = pci_get_domain_bus_and_slot(domain, bus, devfn);
Maybe don't bother with local variables for the things only used once.
e.g.
err_dev = pci_get_domain_bus_and_slot(domain, bus, PCI_DEVFN(slot, func));
and possibly the same for err_type.
I don't mind though if you prefer to use locals for everything.
> break;
> + }
> case PCI_EXP_DPC_STATUS_TRIGGER_RSN_IN_EXT:
> ext_reason = status & PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT;
> pci_warn(pdev, "containment event, status:%#06x: %s detected\n",
>
> >
> > Is there any chance that this might return NULL? Feels like maybe that's
> > only a possibility on a broken setup, but I'm not sure of all the wonderful
> > races around hotplug and DPC occurring before the OS has caught up.
>
> Surprise Down events are handled separately in
> dpc_handle_surprise_removal() and won't reach dpc_process_error().
> Please correct me if I missed anything.
Probably fine. I just didn't check particularly closely.
Jonathan
>
> Thanks for valuable comments.
>
> Best Regards,
> Shuai
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