On 11/3/2026 1:45 AM, Lukas Wunner wrote:
> Certain Intel and AMD Root Ports are known to populate the Error Source ID
> register with an invalid value. The AER driver seeks to recognize such
> buggy silicon by assuming invalidity if the bus number is zero. It then
> searches for the error-signaling device in the hierarchy below the Root
> Port. This was introduced by commit 28eb27cf0839 ("PCI AER: support
> invalid error source IDs").
>
> Alex has provided dmesg output which shows an invalid Error Source ID with
> a non-zero bus number. The AER driver's heuristic fails to recognize its
> invalidity:
>
> pcieport 0000:00:07.1: AER: Correctable Error message received from
> 0000:01:00.0 (no details found)
>
> The Root Port at 0000:00:07.1 has subordinate bus 04, so an error source
> on bus 01 is obviously invalid. The range of subordinate buses is cached
> and checking against it is cheap.
>
> Do that instead of relying on a heuristic. Emit a message when an invalid
> Error Source ID is detected to alert silicon validation engineers.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=222095
> Tested-by: Alex Deucher <[email protected]>
> Signed-off-by: Lukas Wunner <[email protected]>
> ---
> drivers/pci/pci.h | 7 ++++++-
> drivers/pci/pcie/aer.c | 33 +++++++++++++++++++++++++--------
> drivers/pci/pcie/rcec.c | 14 ++++++++++++++
> 3 files changed, 45 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 77efa4c5c960..aa392bb6a482 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -871,6 +871,9 @@ static inline bool pci_dev_binding_disallowed(struct
> pci_dev *dev)
> * @id: Value from register PCI_ERR_ROOT_ERR_SRC
> * @severity: AER severity, 0-UNCOR Non-fatal, 1-UNCOR fatal, 2-COR
> * @root_ratelimit_print: Flag to log or not log the root's error.
> 0=NotLog/1=Log
> + * @id_valid: Whether @id is a valid value. Some Root Ports report an
> invalid
> + * Error Source ID, necessitating a search for the error-signaling device
> + * in the hierarchy below the Root Port.
> * @multi_error_valid: If multiple errors are reported
> * @first_error: First reported error
> * @__pad2: Padding for alignment
> @@ -893,7 +896,8 @@ struct aer_err_info {
>
> unsigned int severity:2;
> unsigned int root_ratelimit_print:1;
> - unsigned int __pad1:4;
> + unsigned int __pad1:3;
> + unsigned int id_valid:1;
> unsigned int multi_error_valid:1;
>
> unsigned int first_error:5;
> @@ -955,6 +959,7 @@ void pcie_link_rcec(struct pci_dev *rcec);
> void pcie_walk_rcec(struct pci_dev *rcec,
> int (*cb)(struct pci_dev *, void *),
> void *userdata);
> +bool pci_rcec_associated(struct pci_dev *rcec, u16 id);
> #else
> static inline void pci_rcec_init(struct pci_dev *dev) { }
> static inline void pci_rcec_exit(struct pci_dev *dev) { }
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index d492c7ce01e1..9957c36bf215 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -951,12 +951,13 @@ static void aer_print_source(struct pci_dev *dev,
> struct aer_err_info *info,
> {
> u16 source = info->id;
>
> - pci_info(dev, "%s%s Error message%s from %04x:%02x:%02x.%d%s\n",
> + pci_info(dev, "%s%s Error message%s from %04x:%02x:%02x.%d%s%s\n",
> info->multi_error_valid ? "Multiple " : "",
> aer_error_severity_string[info->severity],
> info->multi_error_valid ? "s received, first one" : "
> received",
> pci_domain_nr(dev->bus), PCI_BUS_NUM(source),
> PCI_SLOT(source), PCI_FUNC(source),
> + info->id_valid ? "" : " (invalid source)",
> found ? "" : " (no details found)");
> }
>
> @@ -1146,6 +1147,24 @@ static int add_error_device(struct aer_err_info
> *e_info, struct pci_dev *dev)
> return 0;
> }
>
> +static bool source_id_valid(struct pci_dev *root, u16 id)
> +{
> + /* The Root Port or RCEC can itself be a valid Error Source */
> + if (pci_dev_id(root) == id)
> + return true;
> +
> + /* For RCECs, @id shall be in range of its associated buses/devices */
> + if (pci_pcie_type(root) == PCI_EXP_TYPE_RC_EC)
> + return pci_rcec_associated(root, id);
> +
> + /* For Root Ports, @id shall be in range of its subordinate buses */
> + if (!root->subordinate)
> + return false;
> +
> + return root->subordinate->busn_res.start <= PCI_BUS_NUM(id) &&
> + root->subordinate->busn_res.end >= PCI_BUS_NUM(id);
> +}
> +
> /**
> * is_error_source - check whether the device is source of reported error
> * @dev: pointer to pci_dev to be checked
> @@ -1157,11 +1176,8 @@ static bool is_error_source(struct pci_dev *dev,
> struct aer_err_info *e_info)
> u32 status, mask;
> u16 reg16;
>
> - /*
> - * When bus ID is equal to 0, it might be a bad ID
> - * reported by Root Port.
> - */
> - if ((PCI_BUS_NUM(e_info->id) != 0) &&
> + /* Some Root Ports report an invalid Error Source ID */
> + if (e_info->id_valid &&
> !(dev->bus->bus_flags & PCI_BUS_FLAGS_NO_AERSID)) {
> /* Device ID match? */
> if (e_info->id == pci_dev_id(dev))
> @@ -1174,8 +1190,7 @@ static bool is_error_source(struct pci_dev *dev, struct
> aer_err_info *e_info)
>
> /*
> * When either
> - * 1) bus ID is equal to 0. Some ports might lose the bus
> - * ID of error source id;
> + * 1) Error Source ID register is invalid;
> * 2) bus flag PCI_BUS_FLAGS_NO_AERSID is set
> * 3) There are multiple errors and prior ID comparing fails;
> * We check AER status registers to find possible reporter.
> @@ -1566,6 +1581,8 @@ static void aer_isr_one_error_type(struct pci_dev *root,
> {
> bool found;
>
> + info->id_valid = source_id_valid(root, info->id);
> +
> found = find_source_device(root, info);
nit: Updated the kernel-doc help of find_source_device() to include id_valid.
>
> /*
> diff --git a/drivers/pci/pcie/rcec.c b/drivers/pci/pcie/rcec.c
> index 2bf6d9d549ba..609d656300fa 100644
> --- a/drivers/pci/pcie/rcec.c
> +++ b/drivers/pci/pcie/rcec.c
> @@ -21,6 +21,20 @@ struct walk_rcec_data {
> void *user_data;
> };
>
> +bool pci_rcec_associated(struct pci_dev *rcec, u16 id)
> +{
> + if (!rcec->rcec_ea)
> + return false;
> +
> + if (rcec->bus->number == PCI_BUS_NUM(id)) {
> + unsigned long bitmap = rcec->rcec_ea->bitmap;
> + return test_bit(PCI_SLOT(id), &bitmap);
> + }
> +
> + return rcec->rcec_ea->nextbusn <= PCI_BUS_NUM(id) &&
> + rcec->rcec_ea->lastbusn >= PCI_BUS_NUM(id);
> +}
> +
> static bool rcec_assoc_rciep(struct pci_dev *rcec, struct pci_dev *rciep)
> {
> unsigned long bitmap = rcec->rcec_ea->bitmap;
Reviewed-by: Kuppuswamy Sathyanarayanan
<[email protected]>
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
