Re: [PATCH 3/4 v2] ACPI: extlog: Trace CPER PCI Express Error Section

Fabio M. De Francesco
2025-06-02T18:11:20Z

On Tuesday, April 29, 2025 8:02:42 PM Central European Summer Time Yazen Ghannam wrote:
> On Tue, Apr 29, 2025 at 07:21:08PM +0200, Fabio M. De Francesco wrote:
> > I/O Machine Check Arcitecture events may signal failing PCIe components
> > or links. The AER event contains details on what was happening on the wire
> > when the error was signaled.
> >
> > Trace the CPER PCIe Error section (UEFI v2.10, Appendix N.2.7) reported
> > by the I/O MCA.
> >
> > Cc: Dan Williams <dan.j.williams@intel.com>
> > Signed-off-by: Fabio M. De Francesco <fabio.m.de.francesco@linux.intel.com>
> > ---
> > drivers/acpi/acpi_extlog.c | 30 ++++++++++++++++++++++++++++++
> > drivers/pci/pcie/aer.c | 2 +-
> > include/linux/aer.h | 13 +++++++++++--
> > 3 files changed, 42 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/acpi/acpi_extlog.c b/drivers/acpi/acpi_extlog.c
> > index caca6ccd6e99..7d7a813169f1 100644
> > --- a/drivers/acpi/acpi_extlog.c
> > +++ b/drivers/acpi/acpi_extlog.c
> > @@ -131,6 +131,32 @@ static int print_extlog_rcd(const char *pfx,
> > return 1;
> > }
> >
> > +static void extlog_print_pcie(struct cper_sec_pcie *pcie_err,
> > + int severity)
> > +{
> > + struct aer_capability_regs *aer;
> > + struct pci_dev *pdev;
> > + unsigned int devfn;
> > + unsigned int bus;
> > + int aer_severity;
> > + int domain;
> > +
> > + if (pcie_err->validation_bits & CPER_PCIE_VALID_DEVICE_ID &&
> > + pcie_err->validation_bits & CPER_PCIE_VALID_AER_INFO) {
>
> You can save an indentation level by inverting this check and returning
> early.
>
Nice idea, I'll do it.
>
> > + aer_severity = cper_severity_to_aer(severity);
>
> I think it would help with clarity if all these lines were aligned on
> the "=".
>
> > + aer = (struct aer_capability_regs *)pcie_err->aer_info;
> > + domain = pcie_err->device_id.segment;
> > + bus = pcie_err->device_id.bus;
>
> Many of these variables are passed unchanged to a single function below.
>
> Why not pass them directly to the function?
>
> Even if you split the function parameters across multiple lines, you
> will still have fewer lines. Plus you will not need to allocate the
> variables.
>
I think that the cost is minimal and readability is improved.
>
> > + devfn = PCI_DEVFN(pcie_err->device_id.device,
> > + pcie_err->device_id.function);
> > + pdev = pci_get_domain_bus_and_slot(domain, bus, devfn);
> > + if (!pdev)
> > + return;
>
> Newline here, please.
>
Sure.
>
> > + pci_print_aer(KERN_DEBUG, pdev, aer_severity, aer);
>
> Why use a debug log level?
>
Dan Williams suggested the debug log level commenting v1.
>
> > + pci_dev_put(pdev);
> > + }
> > +}
> > +
> > static int extlog_print(struct notifier_block *nb, unsigned long val,
> > void *data)
> > {
> > @@ -182,6 +208,10 @@ static int extlog_print(struct notifier_block *nb, unsigned long val,
> > if (gdata->error_data_length >= sizeof(*mem))
> > trace_extlog_mem_event(mem, err_seq, fru_id, fru_text,
> > (u8)gdata->error_severity);
> > + } else if (guid_equal(sec_type, &CPER_SEC_PCIE)) {
> > + struct cper_sec_pcie *pcie_err = acpi_hest_get_payload(gdata);
> > +
> > + extlog_print_pcie(pcie_err, gdata->error_severity);
> > } else {
> > void *err = acpi_hest_get_payload(gdata);
> >
> > diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> > index d0ebf7c15afa..627fcf434698 100644
> > --- a/drivers/pci/pcie/aer.c
> > +++ b/drivers/pci/pcie/aer.c
> > @@ -801,7 +801,7 @@ void pci_print_aer(char *level, struct pci_dev *dev, int aer_severity,
> > trace_aer_event(dev_name(&dev->dev), (status & ~mask),
> > aer_severity, tlp_header_valid, &aer->header_log);
> > }
> > -EXPORT_SYMBOL_NS_GPL(pci_print_aer, "CXL");
> > +EXPORT_SYMBOL_GPL(pci_print_aer);
> >
> > /**
> > * add_error_device - list device to be handled
> > diff --git a/include/linux/aer.h b/include/linux/aer.h
> > index 45d0fb2e2e75..737db92e6570 100644
> > --- a/include/linux/aer.h
> > +++ b/include/linux/aer.h
> > @@ -56,17 +56,26 @@ struct aer_capability_regs {
> > #if defined(CONFIG_PCIEAER)
> > int pci_aer_clear_nonfatal_status(struct pci_dev *dev);
> > int pcie_aer_is_native(struct pci_dev *dev);
> > +void pci_print_aer(char *level, struct pci_dev *dev, int aer_severity,
> > + struct aer_capability_regs *aer);
> > #else
> > static inline int pci_aer_clear_nonfatal_status(struct pci_dev *dev)
> > {
> > return -EINVAL;
> > }
> > static inline int pcie_aer_is_native(struct pci_dev *dev) { return 0; }
> > +static inline void pci_print_aer(char *level, struct pci_dev *dev,
> > + int aer_severity,
> > + struct aer_capability_regs *aer)
> > +{ }
>
> I think the "{ }" can just go at the end of the parameters.
>
> > #endif
> >
> > -void pci_print_aer(char *level, struct pci_dev *dev, int aer_severity,
> > - struct aer_capability_regs *aer);
> > +#if defined(CONFIG_ACPI_APEI_PCIEAER)
> > int cper_severity_to_aer(int cper_severity);
> > +#else
> > +static inline int cper_severity_to_aer(int cper_severity) { return 0; }
>
> This may have an unintentional side effect.
>
> '0' means AER_NONFATAL.
>
> So the function will return that the error is an uncorrectable AER error
> that is potentially recoverable. At a minimum, this will incorrectly
> classify the error for data collection, and it could cause incorrect
> handling.
>
> I guess the risk is minimal, since CONFIG_ACPI_APEI_PCIEAER will likely
> be enabled on systems that would use this.
>
Noted. Kconfig will select CONFIG_ACPI_APEI_PCIEAER.
>
> Thanks,
> Yazen
>

Thanks,

Fabio