ON-15198: Enable differing values for max_sbufs in user and kernel space

Users should be able to reload the onload kernel module without having
to recompile their user space program. As such, there will be differing
views of `CI_EFCT_MAX_SUPERBUFS` from user and kernel space due to this
patch. This case is now handled in the kernel module without returning
an error.

src/include/ci/internal/seq.h

@@ -18,4 +18,4 @@
 #define SEQ_MIN(x, y)           (SEQ_LE(x, y) ? (x) : (y))
 #define SEQ_MAX(x, y)           (SEQ_LE(x, y) ? (y) : (x))
 
-#endif /* __CI_INTERNAL_SEQ_H__ */
+#endif /* __CI_INTERNAL_SEQ_H__ */

src/lib/efrm/efrm_efct_rxq.c

@@ -189,10 +189,15 @@ int efrm_rxq_refresh(struct efrm_efct_rxq *rxq, unsigned long superbufs,
 	struct xlnx_efct_hugepage spare_page = {};
 	size_t i;
 	int rc = 0;
+	bool is_sbuf_err_logged = false;
+	unsigned n_hugepages = CI_MIN(max_superbufs, (unsigned)CI_EFCT_MAX_SUPERBUFS) /
+                         CI_EFCT_SUPERBUFS_PER_PAGE;
 
 	if (max_superbufs != CI_EFCT_MAX_SUPERBUFS) {
-		/* Could be supported without much difficulty, but no need for now */
-		return -EINVAL;
+		EFRM_TRACE("max_superbufs: %u passed in by user not equal to kernel's: %u. "
+		           "Ensure you do not create enough apps to donate more than %u "
+		           "superbufs!", max_superbufs, CI_EFCT_MAX_SUPERBUFS,
+		           n_hugepages * CI_EFCT_SUPERBUFS_PER_PAGE);
 	}
 
 	pages = kmalloc_array(sizeof(pages[0]), CI_EFCT_MAX_HUGEPAGES,
@@ -218,11 +223,11 @@ int efrm_rxq_refresh(struct efrm_efct_rxq *rxq, unsigned long superbufs,
 			break;
 		}
 	}
-	for (i = 0; i < CI_EFCT_MAX_HUGEPAGES; i += REFRESH_BATCH_SIZE) {
+	for (i = 0; i < n_hugepages; i += REFRESH_BATCH_SIZE) {
 		uint64_t local_current[REFRESH_BATCH_SIZE];
 		size_t j;
 		size_t n = min((size_t)REFRESH_BATCH_SIZE,
-		               CI_EFCT_MAX_HUGEPAGES - i);
+		               n_hugepages - i);
 		bool changes = false;
 
 		if (copy_from_user(local_current, user_current + i,
@@ -254,6 +259,13 @@ int efrm_rxq_refresh(struct efrm_efct_rxq *rxq, unsigned long superbufs,
 		if (pages[i].page != NULL) {
 			put_page(pages[i].page);
 			fput(pages[i].file);
+			if (i > n_hugepages && !is_sbuf_err_logged) {
+				EFRM_ERR("More than %d superbufs have been donated. User max: %u, "
+				         "kernel max: %u. There are likely too many applications running.",
+				         n_hugepages * CI_EFCT_SUPERBUFS_PER_PAGE, max_superbufs,
+				         CI_EFCT_MAX_SUPERBUFS);
+				is_sbuf_err_logged = true;
+			}
 		}
 	}