fast-get: fix userspace thread detection

Checking number of memory domain partitions in thread's domain to
determine whether it's a userspace thread isn't reliable and is a
layering violation. Instead check the K_USER flag which indicates
exactly that.

Suggested-by: Adrian Warecki <adrian.warecki@intel.com>
Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>

Author: lyakh

posix/include/rtos/kernel.h

@@ -28,6 +28,11 @@ typedef struct {
 
 #define Z_TIMEOUT_MS(t) ((k_timeout_t) { .ticks = clock_ms_to_ticks(PLATFORM_DEFAULT_CLOCK, t) })
 
+static inline bool thread_is_userspace(struct k_thread *thread)
+{
+	return false;
+}
+
 static inline void k_sleep(k_timeout_t timeout)
 {
 	wait_delay(timeout.ticks);

zephyr/include/rtos/kernel.h

@@ -8,4 +8,9 @@
 
 #include <zephyr/kernel.h>
 
+static inline bool thread_is_userspace(struct k_thread *thread)
+{
+	return !!(thread->base.user_options & K_USER);
+}
+
 #endif /* __ZEPHYR_RTOS_KERNEL_H__ */

zephyr/lib/fast-get.c

@@ -189,8 +189,7 @@ const void *fast_get(struct k_heap *heap, const void *dram_ptr, size_t size)
 		 * We only get there for large buffers, since small buffers with
 		 * enabled userspace don't create fast-get entries
 		 */
-		if (mdom->num_partitions > 1) {
-			/* A userspace thread makes the request */
+		if (thread_is_userspace(k_current_get())) {
 			if (mdom != entry->mdom &&
 			    !fast_get_partition_exists(k_current_get(), ret,
 						       ALIGN_UP(size, CONFIG_MM_DRV_PAGE_SIZE))) {