cxl: Add kernel APIs to get & set the max irqs per context

These APIs will be used by the Mellanox CX4 support. While they function
standalone to configure existing behaviour, their primary purpose is to
allow the Mellanox driver to inform the cxl driver of a hardware
limitation, which will be used in a future patch.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Reviewed-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/cxl/api.c

@@ -447,3 +447,30 @@ ssize_t cxl_read_adapter_vpd(struct pci_dev *dev, void *buf, size_t count)
 	return cxl_ops->read_adapter_vpd(afu->adapter, buf, count);
 }
 EXPORT_SYMBOL_GPL(cxl_read_adapter_vpd);
+
+int cxl_set_max_irqs_per_process(struct pci_dev *dev, int irqs)
+{
+	struct cxl_afu *afu = cxl_pci_to_afu(dev);
+	if (IS_ERR(afu))
+		return -ENODEV;
+
+	if (irqs > afu->adapter->user_irqs)
+		return -EINVAL;
+
+	/* Limit user_irqs to prevent the user increasing this via sysfs */
+	afu->adapter->user_irqs = irqs;
+	afu->irqs_max = irqs;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(cxl_set_max_irqs_per_process);
+
+int cxl_get_max_irqs_per_process(struct pci_dev *dev)
+{
+	struct cxl_afu *afu = cxl_pci_to_afu(dev);
+	if (IS_ERR(afu))
+		return -ENODEV;
+
+	return afu->irqs_max;
+}
+EXPORT_SYMBOL_GPL(cxl_get_max_irqs_per_process);

include/misc/cxl.h

@@ -166,6 +166,16 @@ void cxl_psa_unmap(void __iomem *addr);
 /*  Get the process element for this context */
 int cxl_process_element(struct cxl_context *ctx);
 
+/*
+ * Limit the number of interrupts that a single context can allocate via
+ * cxl_start_work. If using the api with a real phb, this may be used to
+ * request that additional default contexts be created when allocating
+ * interrupts via pci_enable_msix_range. These will be set to the same running
+ * state as the default context, and if that is running it will reuse the
+ * parameters previously passed to cxl_start_context for the default context.
+ */
+int cxl_set_max_irqs_per_process(struct pci_dev *dev, int irqs);
+int cxl_get_max_irqs_per_process(struct pci_dev *dev);
 
 /*
  * These calls allow drivers to create their own file descriptors and make them