cxl: Route eeh events to all drivers in cxl_pci_error_detected()

Fix a boundary condition where in some cases an eeh event that results
in card reset isn't passed on to a driver attached to the virtual PCI
device associated with a slice. This will happen in case when a slice
attached device driver returns a value other than
PCI_ERS_RESULT_NEED_RESET from the eeh error_detected() callback. This
would result in an early return from cxl_pci_error_detected() and
other drivers attached to other AFUs on the card wont be notified.

The patch fixes this by making sure that all slice attached
device-drivers are notified and the return values from
error_detected() callback are aggregated in a scheme where request for
'disconnect' trumps all and 'none' trumps 'need_reset'.

Fixes: 9e8df8a219 ("cxl: EEH support")
Cc: stable@vger.kernel.org # v4.3+
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/cxl/pci.c

@@ -2057,7 +2057,7 @@ static pci_ers_result_t cxl_pci_error_detected(struct pci_dev *pdev,
 {
 	struct cxl *adapter = pci_get_drvdata(pdev);
 	struct cxl_afu *afu;
-	pci_ers_result_t result = PCI_ERS_RESULT_NEED_RESET;
+	pci_ers_result_t result = PCI_ERS_RESULT_NEED_RESET, afu_result;
 	int i;
 
 	/* At this point, we could still have an interrupt pending.
@@ -2162,15 +2162,18 @@ static pci_ers_result_t cxl_pci_error_detected(struct pci_dev *pdev,
 	for (i = 0; i < adapter->slices; i++) {
 		afu = adapter->afu[i];
 
-		result = cxl_vphb_error_detected(afu, state);
-
-		/* Only continue if everyone agrees on NEED_RESET */
-		if (result != PCI_ERS_RESULT_NEED_RESET)
-			return result;
+		afu_result = cxl_vphb_error_detected(afu, state);
 
 		cxl_context_detach_all(afu);
 		cxl_ops->afu_deactivate_mode(afu, afu->current_mode);
 		pci_deconfigure_afu(afu);
+
+		/* Disconnect trumps all, NONE trumps NEED_RESET */
+		if (afu_result == PCI_ERS_RESULT_DISCONNECT)
+			result = PCI_ERS_RESULT_DISCONNECT;
+		else if ((afu_result == PCI_ERS_RESULT_NONE) &&
+			 (result == PCI_ERS_RESULT_NEED_RESET))
+			result = PCI_ERS_RESULT_NONE;
 	}
 
 	/* should take the context lock here */