linux-kernel - RE: [PATCH v10 07/17] CXL/PCI: Introduce CXL uncorrectable protocol error recovery

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Message-ID: <8b09bb6b1c4d4363996368b67a574e1d@huawei.com>
Date: Fri, 27 Jun 2025 12:27:49 +0000
From: Shiju Jose <shiju.jose@...wei.com>
To: Terry Bowman <terry.bowman@....com>, "dave@...olabs.net"
	<dave@...olabs.net>, Jonathan Cameron <jonathan.cameron@...wei.com>,
	"dave.jiang@...el.com" <dave.jiang@...el.com>, "alison.schofield@...el.com"
	<alison.schofield@...el.com>, "dan.j.williams@...el.com"
	<dan.j.williams@...el.com>, "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"ming.li@...omail.com" <ming.li@...omail.com>,
	"Smita.KoralahalliChannabasappa@....com"
	<Smita.KoralahalliChannabasappa@....com>, "rrichter@....com"
	<rrichter@....com>, "dan.carpenter@...aro.org" <dan.carpenter@...aro.org>,
	"PradeepVineshReddy.Kodamati@....com" <PradeepVineshReddy.Kodamati@....com>,
	"lukas@...ner.de" <lukas@...ner.de>, "Benjamin.Cheatham@....com"
	<Benjamin.Cheatham@....com>, "sathyanarayanan.kuppuswamy@...ux.intel.com"
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, "linux-cxl@...r.kernel.org"
	<linux-cxl@...r.kernel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: RE: [PATCH v10 07/17] CXL/PCI: Introduce CXL uncorrectable protocol
 error recovery

>-----Original Message-----
>From: Terry Bowman <terry.bowman@....com>
>Sent: 26 June 2025 23:43
>To: dave@...olabs.net; Jonathan Cameron <jonathan.cameron@...wei.com>;
>dave.jiang@...el.com; alison.schofield@...el.com; dan.j.williams@...el.com;
>bhelgaas@...gle.com; Shiju Jose <shiju.jose@...wei.com>;
>ming.li@...omail.com; Smita.KoralahalliChannabasappa@....com;
>rrichter@....com; dan.carpenter@...aro.org;
>PradeepVineshReddy.Kodamati@....com; lukas@...ner.de;
>Benjamin.Cheatham@....com;
>sathyanarayanan.kuppuswamy@...ux.intel.com; terry.bowman@....com;
>linux-cxl@...r.kernel.org
>Cc: linux-kernel@...r.kernel.org; linux-pci@...r.kernel.org
>Subject: [PATCH v10 07/17] CXL/PCI: Introduce CXL uncorrectable protocol error
>recovery
>
>Create cxl_do_recovery() to provide uncorrectable protocol error (UCE)
>handling. Follow similar design as found in PCIe error driver,
>pcie_do_recovery(). One difference is cxl_do_recovery() will treat all UCEs as
>fatal with a kernel panic. This is to prevent corruption on CXL memory.
>
>Export the PCI error driver's merge_result() to CXL namespace. Introduce
>PCI_ERS_RESULT_PANIC and add support in merge_result() routine. This will be
>used by CXL to panic the system in the case of uncorrectable protocol errors. PCI
>error handling is not currently expected to use the PCI_ERS_RESULT_PANIC.
>
>Copy pci_walk_bridge() to cxl_walk_bridge(). Make a change to walk the first
>device in all cases.
>
>Copy the PCI error driver's report_error_detected() to
>cxl_report_error_detected().
>Note, only CXL Endpoints and RCH Downstream Ports(RCH DSP) are currently
>supported. Add locking for PCI device as done in PCI's report_error_detected().
>This is necessary to prevent the RAS registers from disappearing before logging
>is completed.
>
>Call panic() to halt the system in the case of uncorrectable errors (UCE) in
>cxl_do_recovery(). Export pci_aer_clear_fatal_status() for CXL to use if a UCE is
>not found. In this case the AER status must be cleared and uses
>pci_aer_clear_fatal_status().
>
>Signed-off-by: Terry Bowman <terry.bowman@....com>
>---
> drivers/cxl/core/native_ras.c | 44 +++++++++++++++++++++++++++++++++++
> drivers/pci/pcie/cxl_aer.c    |  3 ++-
> drivers/pci/pcie/err.c        |  8 +++++--
> include/linux/aer.h           | 11 +++++++++
> include/linux/pci.h           |  3 +++
> 5 files changed, 66 insertions(+), 3 deletions(-)
>
[...]
>
> void pci_print_aer(struct pci_dev *dev, int aer_severity, diff --git
>a/include/linux/pci.h b/include/linux/pci.h index 79326358f641..16a8310e0373
>100644
>--- a/include/linux/pci.h
>+++ b/include/linux/pci.h
>@@ -868,6 +868,9 @@ enum pci_ers_result {
>
> 	/* No AER capabilities registered for the driver */
> 	PCI_ERS_RESULT_NO_AER_DRIVER = (__force pci_ers_result_t) 6,
>+
>+	/* System is unstable, panic. Is CXL specific  */
>+	PCI_ERS_RESULT_PANIC = (__force pci_ers_result_t) 7,
Extra space is present after casting?
> };
>
> /* PCI bus error event callbacks */
>--
>2.34.1