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Sashiko AI review found 1 potential issue(s) to consider: > - [High] CXL protocol errors on RCD Endpoints bypass the AER-CXL kfifo, leading to dropped correctable errors and UCE race conditions. > -- > > commit 6e514f9fb46669ba2eab05ced2511b382df00bce > Author: Terry Bowman > > PCI: Establish common CXL Port protocol error flow > > This commit establishes a single CXL protocol error path shared by Virtual > Hierarchy and Restricted CXL Host topologies. It routes CXL protocol errors, > gated by is_cxl_error(), through an AER-CXL kfifo to a core consumer for > logging and recovery to ensure synchronization. > >> diff --git a/drivers/pci/pcie/aer_cxl_rch.c b/drivers/pci/pcie/aer_cxl_rch.c >> --- a/drivers/pci/pcie/aer_cxl_rch.c >> +++ b/drivers/pci/pcie/aer_cxl_rch.c > [ ... ] >> -void cxl_rch_handle_error(struct pci_dev *dev, struct aer_err_info *info) >> +bool cxl_rch_handle_error(struct pci_dev *dev, struct aer_err_info *info) >> { >> + struct cxl_rch_error_ctx ctx = { .info = info }; >> + >> /* >> - * Internal errors of an RCEC indicate an AER error in an >> - * RCH's downstream port. Check and handle them in the CXL.mem >> - * device driver. >> + * An RCEC AER internal error indicates an error in an >> + * associated RCH Downstream Port or RCD device or both. >> + * Forward to the cxl_core module for handling. >> */ >> if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC && >> is_aer_internal_error(info)) >> - pcie_walk_rcec(dev, cxl_rch_handle_error_iter, info); >> + pcie_walk_rcec(dev, cxl_rch_handle_error_iter, &ctx); >> + >> + return ctx.enqueued; >> } > > [Severity: High] > Does this check accidentally skip errors logged directly by the RCD itself? > No. RCH and RCD errors are reported by the platform to the AER agent using RCECs. SW must 'discover' which RCiEP(s) managed by the RCEC have an error. > When an RCD detects an error, it logs it in its own AER capability and the > RCEC raises the interrupt. The AER driver's find_source_device() then walks > the RCEC's children, finds the RCD with the set AER status, and calls > handle_error_source() with the RCD device. > > Because this condition strictly checks for PCI_EXP_TYPE_RC_EC, it intercepts > errors from the RCEC itself (like RCH Downstream Port errors), but bypasses > handling when the RCD device itself is passed in. > >> diff --git a/drivers/pci/pcie/aer_cxl_vh.c b/drivers/pci/pcie/aer_cxl_vh.c >> --- a/drivers/pci/pcie/aer_cxl_vh.c >> +++ b/drivers/pci/pcie/aer_cxl_vh.c > [ ... ] >> @@ -54,8 +54,22 @@ bool is_cxl_error(struct pci_dev *pdev, struct aer_err_info *info) >> if (!info || !info->is_cxl) >> return false; >> >> - if (pci_pcie_type(pdev) != PCI_EXP_TYPE_ENDPOINT) >> + /* >> + * RCD (PCI_EXP_TYPE_RC_END) is not included here because RCDs >> + * report errors on behalf of upstream RCH Downstream Port and thus >> + * require a unique discovery detailed in CXL4.0 spec (12.2.1.1). >> + * The RCH device error discovery and RCD forwarding flow begins >> + * in cxl_rch_handle_error(). >> + */ >> + switch (pci_pcie_type(pdev)) { >> + case PCI_EXP_TYPE_ENDPOINT: >> + case PCI_EXP_TYPE_ROOT_PORT: >> + case PCI_EXP_TYPE_UPSTREAM: >> + case PCI_EXP_TYPE_DOWNSTREAM: >> + break; >> + default: >> return false; >> + } >> >> return is_aer_internal_error(info); >> } > > [Severity: High] > Since RCDs are excluded here, does this bypass the AER-CXL kfifo entirely for > RCD protocol errors? > is_cxl_error() is used to verify VH devices and is intentionally not used for RCH/RCDs. Below is the flow for RCH/RCDs: RCEC internal error → cxl_rch_handle_error(RC_EC) → pcie_walk_rcec() → cxl_rch_handle_error_iter(RCD) → is_cxl_mem_dev(RCD) && cxl_error_is_native(RCD) → cxl_forward_error(RCD, info) ← ENQUEUED to the kfifo CXL r4.0 12.2.1.1 addresses RCH/RCD error handling and provides contrast to VH mode. -Terry > As noted above, cxl_rch_handle_error() skips the RCD device. With the RCD > also falling through to the default case here and returning false, these > errors are never enqueued. > > This results in correctable errors being silently dropped without being > traced or cleared (as the legacy cor_error_detected fallback was removed). > For uncorrectable errors, it bypasses the kfifo's synchronization, defeating > the race-condition fix and leaving the system vulnerable to teardown races. >