[PATCH] cxl: Handle num_of_processes larger than can fit in the SPA

[Ian Munsie]

From: Ian Munsie <imunsie at au1.ibm.com>

num_of_process is a 16 bit field, theoretically allowing an AFU to
support 16K processes, however the scheduled process area currently has
a maximum size of 1MB, which limits the maximum number of processes to
7704.

Some AFUs may not necessarily care what the limit is and just want to be
able to use the maximum by setting the field to 16K. To allow these to
work, detect this situation and use the maximum size for the SPA.

Downgrade the WARN_ON to a dev_warn.

Signed-off-by: Ian Munsie <imunsie at au1.ibm.com>
---
 drivers/misc/cxl/native.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/cxl/native.c b/drivers/misc/cxl/native.c
index 387fcbd..b8b547a 100644
--- a/drivers/misc/cxl/native.c
+++ b/drivers/misc/cxl/native.c
@@ -185,16 +185,25 @@ static int spa_max_procs(int spa_size)
 
 int cxl_alloc_spa(struct cxl_afu *afu)
 {
+	unsigned spa_size;
+
 	/* Work out how many pages to allocate */
 	afu->native->spa_order = 0;
 	do {
 		afu->native->spa_order++;
-		afu->native->spa_size = (1 << afu->native->spa_order) * PAGE_SIZE;
+		spa_size = (1 << afu->native->spa_order) * PAGE_SIZE;
+
+		if (spa_size > 0x100000) {
+			dev_warn(&afu->dev, "num_of_processes too large for the SPA, limiting to %i (0x%x)\n",
+					afu->native->spa_max_procs, afu->native->spa_size);
+			afu->num_procs = afu->native->spa_max_procs;
+			break;
+		}
+
+		afu->native->spa_size = spa_size;
 		afu->native->spa_max_procs = spa_max_procs(afu->native->spa_size);
 	} while (afu->native->spa_max_procs < afu->num_procs);
 
-	WARN_ON(afu->native->spa_size > 0x100000); /* Max size supported by the hardware */
-
 	if (!(afu->native->spa = (struct cxl_process_element *)
 	      __get_free_pages(GFP_KERNEL | __GFP_ZERO, afu->native->spa_order))) {
 		pr_err("cxl_alloc_spa: Unable to allocate scheduled process area\n");
-- 
2.1.4