[PATCH v14 30/34] PCI/AER: Dequeue forwarded CXL error

[Terry Bowman <terry.bowman@amd.com>]

The AER driver now forwards CXL protocol errors to the CXL driver via a
kfifo. The CXL driver must consume these work items and initiate protocol
error handling while ensuring the device's RAS mappings remain valid
throughout processing.

Implement cxl_proto_err_work_fn() to dequeue work items forwarded by the
AER service driver. Lock the parent CXL Port device to ensure the CXL
device's RAS registers are accessible during handling. Add pdev reference-put
to match reference-get in AER driver. This will ensure pdev access after
kfifo dequeue. These changes apply to CXL Ports and CXL Endpoints.

Signed-off-by: Terry Bowman <terry.bowman@amd.com>

---

Changes in v13->v14:
- Update commit title's prefix (Bjorn)
- Add pdev ref get in AER driver before enqueue and add pdev ref put in
  CXL driver after dequeue and handling (Dan)
- Removed handling to simplify patch context (Terry)

Changes in v12->v13:
- Add cxlmd lock using guard() (Terry)
- Remove exporting of unused function, pci_aer_clear_fatal_status() (Dave Jiang)
- Change pr_err() calls to ratelimited. (Terry)
- Update commit message. (Terry)
- Remove namespace qualifier from pcie_clear_device_status()
  export (Dave Jiang)
- Move locks into cxl_proto_err_work_fn() (Dave)
- Update log messages in cxl_forward_error() (Ben)

Changes in v11->v12:
- Add guard for CE case in cxl_handle_proto_error() (Dave)

Changes in v10->v11:
- Reword patch commit message to remove RCiEP details (Jonathan)
- Add #include <linux/bitfield.h> (Terry)
- is_cxl_rcd() - Fix short comment message wrap  (Jonathan)
- is_cxl_rcd() - Combine return calls into 1  (Jonathan)
- cxl_handle_proto_error() - Move comment earlier  (Jonathan)
- Use FIELD_GET() in discovering class code (Jonathan)
- Remove BDF from cxl_proto_err_work_data. Use 'struct
pci_dev *' (Dan)
---
 drivers/cxl/core/core.h       |  3 ++
 drivers/cxl/core/port.c       |  6 +--
 drivers/cxl/core/ras.c        | 98 +++++++++++++++++++++++++++++++----
 drivers/pci/pcie/aer_cxl_vh.c |  1 +
 4 files changed, 94 insertions(+), 14 deletions(-)

diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
index 306762a15dc0..39324e1b8940 100644
--- a/drivers/cxl/core/core.h
+++ b/drivers/cxl/core/core.h
@@ -169,6 +169,9 @@ static inline void cxl_handle_rdport_errors(struct cxl_dev_state *cxlds) { }
 #endif /* CONFIG_CXL_RAS */
 
 int cxl_gpf_port_setup(struct cxl_dport *dport);
+struct cxl_port *find_cxl_port(struct device *dport_dev,
+			       struct cxl_dport **dport);
+struct cxl_port *find_cxl_port_by_uport(struct device *uport_dev);
 
 struct cxl_hdm;
 int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index a535e57360e0..0bec10be5d56 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -1335,8 +1335,8 @@ static struct cxl_port *__find_cxl_port(struct cxl_find_port_ctx *ctx)
 	return NULL;
 }
 
-static struct cxl_port *find_cxl_port(struct device *dport_dev,
-				      struct cxl_dport **dport)
+struct cxl_port *find_cxl_port(struct device *dport_dev,
+			       struct cxl_dport **dport)
 {
 	struct cxl_find_port_ctx ctx = {
 		.dport_dev = dport_dev,
@@ -1578,7 +1578,7 @@ static int match_port_by_uport(struct device *dev, const void *data)
  * Function takes a device reference on the port device. Caller should do a
  * put_device() when done.
  */
-static struct cxl_port *find_cxl_port_by_uport(struct device *uport_dev)
+struct cxl_port *find_cxl_port_by_uport(struct device *uport_dev)
 {
 	struct device *dev;
 
diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
index bf82880e19b4..0c640b84ad70 100644
--- a/drivers/cxl/core/ras.c
+++ b/drivers/cxl/core/ras.c
@@ -117,17 +117,6 @@ static void cxl_cper_prot_err_work_fn(struct work_struct *work)
 }
 static DECLARE_WORK(cxl_cper_prot_err_work, cxl_cper_prot_err_work_fn);
 
-int cxl_ras_init(void)
-{
-	return cxl_cper_register_prot_err_work(&cxl_cper_prot_err_work);
-}
-
-void cxl_ras_exit(void)
-{
-	cxl_cper_unregister_prot_err_work(&cxl_cper_prot_err_work);
-	cancel_work_sync(&cxl_cper_prot_err_work);
-}
-
 static void cxl_dport_map_ras(struct cxl_dport *dport)
 {
 	struct cxl_register_map *map = &dport->reg_map;
@@ -173,6 +162,44 @@ void devm_cxl_port_ras_setup(struct cxl_port *port)
 }
 EXPORT_SYMBOL_NS_GPL(devm_cxl_port_ras_setup, "CXL");
 
+/*
+ * Return 'struct cxl_port *' parent CXL Port of dev
+ *
+ * Reference count increments returned port on success
+ *
+ * @pdev: Find the parent CXL Port of this device
+ */
+static struct cxl_port *get_cxl_port(struct pci_dev *pdev)
+{
+	switch (pci_pcie_type(pdev)) {
+	case PCI_EXP_TYPE_ROOT_PORT:
+	case PCI_EXP_TYPE_DOWNSTREAM:
+	{
+		struct cxl_dport *dport;
+		struct cxl_port *port = find_cxl_port(&pdev->dev, &dport);
+
+		if (!port) {
+			pci_err(pdev, "Failed to find the CXL device");
+			return NULL;
+		}
+		return port;
+	}
+	case PCI_EXP_TYPE_UPSTREAM:
+	case PCI_EXP_TYPE_ENDPOINT:
+	{
+		struct cxl_port *port = find_cxl_port_by_uport(&pdev->dev);
+
+		if (!port) {
+			pci_err(pdev, "Failed to find the CXL device");
+			return NULL;
+		}
+		return port;
+	}
+	}
+	pci_warn_once(pdev, "Error: Unsupported device type (%#x)", pci_pcie_type(pdev));
+	return NULL;
+}
+
 void cxl_handle_cor_ras(struct device *dev, u64 serial, void __iomem *ras_base)
 {
 	void __iomem *addr;
@@ -316,3 +343,52 @@ pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
 	return PCI_ERS_RESULT_NEED_RESET;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_error_detected, "CXL");
+
+static void cxl_handle_proto_error(struct cxl_proto_err_work_data *err_info)
+{
+}
+
+static void cxl_proto_err_work_fn(struct work_struct *work)
+{
+	struct cxl_proto_err_work_data wd;
+
+	while (cxl_proto_err_kfifo_get(&wd)) {
+		struct pci_dev *pdev __free(pci_dev_put) = wd.pdev;
+
+		if (!pdev) {
+			pr_err_ratelimited("NULL PCI device passed in AER-CXL KFIFO\n");
+			continue;
+		}
+
+		struct cxl_port *port __free(put_cxl_port) = get_cxl_port(pdev);
+		if (!port) {
+			pr_err_ratelimited("Failed to find parent Port device in CXL topology.\n");
+			continue;
+		}
+		guard(device)(&port->dev);
+
+		cxl_handle_proto_error(&wd);
+	}
+}
+
+static struct work_struct cxl_proto_err_work;
+static DECLARE_WORK(cxl_proto_err_work, cxl_proto_err_work_fn);
+
+int cxl_ras_init(void)
+{
+	if (cxl_cper_register_prot_err_work(&cxl_cper_prot_err_work))
+		pr_err("Failed to initialize CXL RAS CPER\n");
+
+	cxl_register_proto_err_work(&cxl_proto_err_work);
+
+	return 0;
+}
+
+void cxl_ras_exit(void)
+{
+	cxl_cper_unregister_prot_err_work(&cxl_cper_prot_err_work);
+	cancel_work_sync(&cxl_cper_prot_err_work);
+
+	cxl_unregister_proto_err_work();
+	cancel_work_sync(&cxl_proto_err_work);
+}
diff --git a/drivers/pci/pcie/aer_cxl_vh.c b/drivers/pci/pcie/aer_cxl_vh.c
index 2189d3c6cef1..0f616f5fafcf 100644
--- a/drivers/pci/pcie/aer_cxl_vh.c
+++ b/drivers/pci/pcie/aer_cxl_vh.c
@@ -48,6 +48,7 @@ void cxl_forward_error(struct pci_dev *pdev, struct aer_err_info *info)
 	};
 
 	guard(rwsem_read)(&cxl_proto_err_kfifo.rw_sema);
+	pci_dev_get(pdev);
 	if (!cxl_proto_err_kfifo.work || !kfifo_put(&cxl_proto_err_kfifo.fifo, wd)) {
 		dev_err_ratelimited(&pdev->dev, "AER-CXL kfifo error");
 		return;
-- 
2.34.1