library_manager: Guard DRAM store/restore with CONFIG_ADSP_IMR_CONTEXT_SAVE

When ADSP IMR context save is disabled (CONFIG_ADSP_IMR_CONTEXT_SAVE=n),
the HP-SRAM and L3 heap memory are lost during PM runtime suspend/resume.
However, the LLEXT library manager state `lib_manager_dram` resides in
the persistent IMR data section (`__imrdata`) and retains stale pointers
(such as `lib_manager_dram.ctx` pointing to the now-invalid L3 heap
address from the first boot).

On resume, `llext_manager_restore_from_dram()` would try to restore
libraries from these stale pointers, causing register window underflows
and fatal exceptions (EXCCAUSE_ILLEGAL) when executing scheduler work
queues on subsequent IPC handling.

Guard `llext_manager_store_to_dram()` and `llext_manager_restore_from_dram()`
with `IS_ENABLED(CONFIG_ADSP_IMR_CONTEXT_SAVE)`. If context save is
disabled, the library manager cleanly re-initializes on resume boot,
forcing libraries to reload correctly.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

src/library_manager/llext_manager_dram.c

@@ -35,6 +35,15 @@ __imrdata static struct lib_manager_dram_storage lib_manager_dram;
 /* Store LLEXT manager context in DRAM to be restored during the next boot. */
 int llext_manager_store_to_dram(void)
 {
+	/*
+	 * If IMR context save is disabled, HP-SRAM and L3 heap memory are lost
+	 * on suspend/resume, but IMR remains persistent. Skip saving to avoid
+	 * restoring stale pointers.
+	 */
+	if (!IS_ENABLED(CONFIG_ADSP_IMR_CONTEXT_SAVE)) {
+		return 0;
+	}
+
 	struct ext_library *_ext_lib = ext_lib_get();
 	unsigned int i, j, k, l, n_lib, n_mod, n_llext, n_sect, n_sym;
 	size_t buf_size;
@@ -161,6 +170,15 @@ int llext_manager_store_to_dram(void)
 
 int llext_manager_restore_from_dram(void)
 {
+	/*
+	 * If IMR context save is disabled, the L3 heap and HP-SRAM memory were lost.
+	 * The saved context will contain stale pointers, so cleanly re-initialize instead.
+	 */
+	if (!IS_ENABLED(CONFIG_ADSP_IMR_CONTEXT_SAVE)) {
+		lib_manager_init();
+		return 0;
+	}
+
 	lib_manager_init();
 
 	struct ext_library *_ext_lib = ext_lib_get();

zephyr/lib/alloc.c

@@ -838,7 +838,11 @@ static int heap_init(void)
 
 		arch_mem_map(l3_heap_start, va, l3_heap_size, K_MEM_PERM_RW | K_MEM_CACHE_WB);
 #endif
-		if (l3_heap_copy.heap.heap) {
+		/*
+		 * If IMR context save is disabled, the L3 heap memory is lost during
+		 * suspend/resume, so do not restore from the stale copy.
+		 */
+		if (IS_ENABLED(CONFIG_ADSP_IMR_CONTEXT_SAVE) && l3_heap_copy.heap.heap) {
 			l3_heap = l3_heap_copy;
 		} else {
 			l3_heap.heap.init_mem = l3_heap_start;