Re: [PATCH v20 2/9] PCI: Establish common CXL Port protocol error flow

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 2 Sep 2026 08:39:26 -0500
Terry Bowman <terry.bowman@amd.com> wrote:

> Establish a single CXL protocol error path shared by CXL Virtual
> Hierarchy (VH) and Restricted CXL Host (RCH) topologies. AER dispatch in
> handle_error_source() routes CXL protocol errors, gated by
> is_cxl_error(), through the AER-CXL kfifo to a cxl_core consumer for
> logging and recovery. Producer and consumer go live together so no CXL
> error is silently dropped across a bisect.
> 
> is_cxl_error() expands from Endpoint-only to also cover Root Port,
> Upstream Port, and Downstream Port. RCDs report on behalf of an upstream
> RCH Downstream Port and instead reach the kfifo via
> cxl_rch_handle_error().
> 
> For uncorrectable errors, cxl_proto_err_wait_for_empty() drains the CXL
> plane (RAS read, panic policy, state clear) before pci_aer_handle_error()
> drives PCIe recovery, so recovery does not tear down RAS iomaps while the
> consumer is still reading them. Correctable errors run asynchronously.
> 
> Panic policy: cxl_do_recovery() panics on a confirmed UCE, and also when
> the RAS registers cannot be mapped -- an unconfirmable UCE is treated
> conservatively as fatal since CXL.mem coherency may be lost. A
> mapped-but-clear status is logged as spurious with no panic.
> 
> to_ras_base() centralizes RAS base lookup (dport->regs.ras for
> Root/Downstream Ports, port->regs.ras otherwise) and provides an
> injection point for RAS status simulation during testing. The
> cxl_cor_error_detected() AER callback is removed; correctable Endpoint
> errors now route through the kfifo like every other CXL protocol error.
> 
> Update cxl_handle_rdport_errors() with locking to prevent dport from
> being freed and RAS from being unmapped.
> 
> At this step cxl_handle_rdport_errors() still dispatches a single
> severity per pass (matching the pre-series baseline). The following
> patch, "cxl/ras: Handle RCH correctable and uncorrectable errors in one
> pass", processes a simultaneously signalled CE and UCE together.
> 
> Co-developed-by: Dan Williams <djbw@kernel.org>
> Signed-off-by: Dan Williams <djbw@kernel.org>
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
> 
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>