vpage: fix free tracking, release partial maps, enable vpages on small-L2 (NVL-S)

zephyr/lib/vpage.c

@@ -296,18 +296,39 @@ __cold static int vpage_init(void)
 		end = l2_end - CONFIG_LIBRARY_REGION_SIZE;
 	} else {
 		/*
-		 * TODO: on demand mapping currently only supports
-		 * cached mappings, so we need to limit vpages to
-		 * physical L2 size for now until support is added to
-		 * Zephyr mm_drv_intel_adsp_mtl_tlb.c and friends
+		 * Small L2 (e.g. NVL-S): the virtual heap and library regions are only
+		 * virtual address space backed on demand, so they need not fit in L2
+		 * together with the vpages. Use the virtual space up to the library
+		 * region (or the end of virtual memory) and cap it below by the
+		 * physical L2 left after the image, as vpages can never use more.
+		 * Pages beyond physical L2 are accessed through the coherent alias
+		 * too, which needs the Zephyr TLB driver to map the uncached alias.
 		 */
-		LOG_WRN("no space left for vpages, start %#lx l2_end %#lx",
-			(unsigned long)start, (unsigned long)l2_end);
+		end = L2_VIRTUAL_SRAM_BASE + L2_VIRTUAL_SRAM_SIZE;
+		if (IS_ENABLED(CONFIG_LIBRARY_MANAGER) && CONFIG_LIBRARY_BASE_ADDRESS < end)
+			end = CONFIG_LIBRARY_BASE_ADDRESS;
+	}
+
+	/* the image or virtual heap may leave no room, don't let this underflow */
+	if (end < start + CONFIG_MM_DRV_PAGE_SIZE) {
+		LOG_WRN("no space left for vpages, start %#lx end %#lx",
+			(unsigned long)start, (unsigned long)end);
 		return -ENOMEM;
 	}
 
 	remaining_ram = end - start;
-	__ASSERT_NO_MSG(remaining_ram >= CONFIG_MM_DRV_PAGE_SIZE);
+	if (end > l2_end) {
+		uintptr_t image_end = adsp_mm_get_unused_l2_start_aligned();
+		size_t phys_left = image_end < l2_end ? l2_end - image_end : 0;
+
+		remaining_ram = MIN(remaining_ram, phys_left);
+	}
+
+	/* revalidate, the physical cap can leave less than a page */
+	if (remaining_ram < CONFIG_MM_DRV_PAGE_SIZE) {
+		LOG_WRN("no physical L2 left for vpages");
+		return -ENOMEM;
+	}
 
 	ret = adsp_add_virtual_memory_region(start, remaining_ram, VIRTUAL_REGION_VPAGES_ATTR);
 	if (ret)

zephyr/test/vpage.c

@@ -34,3 +34,36 @@ ZTEST(sof_boot, vpage)
 
 	vpage_free(p1);
 }
+
+/* Freeing a non-last allocation must not orphan the last tracked element */
+ZTEST(sof_boot, vpage_free_out_of_order)
+{
+	void *a = vpage_alloc(1);
+	void *b = vpage_alloc(1);
+	void *c, *d;
+
+	zassert_not_null(a);
+	zassert_not_null(b);
+
+	/* the check below needs a and b to be neighbours, first fit normally does this */
+	if ((uint8_t *)b != (uint8_t *)a + CONFIG_MM_DRV_PAGE_SIZE) {
+		vpage_free(a);
+		vpage_free(b);
+		ztest_test_skip();
+		return;
+	}
+
+	vpage_free(a);
+
+	/* takes a's page; must not overwrite b's tracking element */
+	c = vpage_alloc(1);
+	zassert_equal(c, a);
+
+	vpage_free(b);
+	vpage_free(c);
+
+	/* if b's element was lost its page is leaked and the 2 page range can't be reused */
+	d = vpage_alloc(2);
+	zassert_equal(d, a, "pages leaked after out of order free");
+	vpage_free(d);
+}