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. Also add a missing check when adding a partition for
the newly allocated entry.

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 +28,12 @@ typedef struct {
 
 #define Z_TIMEOUT_MS(t) ((k_timeout_t) { .ticks = clock_ms_to_ticks(PLATFORM_DEFAULT_CLOCK, t) })
 
+struct k_thread;
+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

@@ -132,6 +132,9 @@ static int fast_get_access_grant(struct k_mem_domain *mdom, void *addr, size_t s
 
 const void *fast_get(struct k_heap *heap, const void *dram_ptr, size_t size)
 {
+#if CONFIG_USERSPACE
+	bool current_is_userspace = thread_is_userspace(k_current_get());
+#endif
 	struct sof_fast_get_data *data = &fast_get_data;
 	uint32_t alloc_flags = SOF_MEM_FLAG_USER;
 	struct sof_fast_get_entry *entry;
@@ -189,8 +192,7 @@ 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 (current_is_userspace) {
 			if (mdom != entry->mdom &&
 			    !fast_get_partition_exists(k_current_get(), ret,
 						       ALIGN_UP(size, CONFIG_MM_DRV_PAGE_SIZE))) {
@@ -235,7 +237,7 @@ const void *fast_get(struct k_heap *heap, const void *dram_ptr, size_t size)
 
 #if CONFIG_USERSPACE
 	entry->mdom = k_current_get()->mem_domain_info.mem_domain;
-	if (size > FAST_GET_MAX_COPY_SIZE) {
+	if (size > FAST_GET_MAX_COPY_SIZE && current_is_userspace) {
 		/* Otherwise we've allocated on thread's heap, so it already has access */
 		int err = fast_get_access_grant(entry->mdom, ret, size);