mmu: arch_mem_map() may no longer fail

Pre-allocation of paging structures is now required, such that
no allocations are ever needed when mapping memory.

Instantiation of new memory domains may still require allocations
unless a common page table is used.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

arch/x86/core/x86_mmu.c

@@ -1084,7 +1084,7 @@ static pentry_t flags_to_entry(uint32_t flags)
 	case K_MEM_CACHE_WB:
 		break;
 	default:
-		return -ENOTSUP;
+		__ASSERT(false, "bad memory mapping flags 0x%x", flags);
 	}
 
 	if ((flags & K_MEM_PERM_RW) != 0U) {
@@ -1103,12 +1103,10 @@ static pentry_t flags_to_entry(uint32_t flags)
 }
 
 /* map new region virt..virt+size to phys with provided arch-neutral flags */
-int arch_mem_map(void *virt, uintptr_t phys, size_t size, uint32_t flags)
+void arch_mem_map(void *virt, uintptr_t phys, size_t size, uint32_t flags)
 {
 	range_map_unlocked(virt, phys, size, flags_to_entry(flags),
 			   MASK_ALL, 0);
-
-	return 0;
 }
 
 #if CONFIG_X86_STACK_PROTECTION

kernel/include/kernel_arch_interface.h

@@ -241,6 +241,13 @@ static inline bool arch_is_in_isr(void);
  * to this API are assumed to be serialized, and indeed all usage will
  * originate from kernel/mm.c which handles virtual memory management.
  *
+ * Architectures are expected to pre-allocate page tables for the entire
+ * address space, as defined by CONFIG_KERNEL_VM_BASE and
+ * CONFIG_KERNEL_VM_SIZE. This operation should never require any kind of
+ * allocation for paging structures.
+ *
+ * Validation of arguments should be done via assertions.
+ *
  * This API is part of infrastructure still under development and may
  * change.
  *
@@ -248,12 +255,8 @@ static inline bool arch_is_in_isr(void);
  * @param addr Page-aligned Source physical address to map
  * @param size Page-aligned size of the mapped memory region in bytes
  * @param flags Caching, access and control flags, see K_MAP_* macros
- * @retval 0 Success
- * @retval -ENOTSUP Unsupported cache mode with no suitable fallback, or
- *	   unsupported flags
- * @retval -ENOMEM Memory for additional paging structures unavailable
  */
-int arch_mem_map(void *dest, uintptr_t addr, size_t size, uint32_t flags);
+void arch_mem_map(void *dest, uintptr_t addr, size_t size, uint32_t flags);
 
 /**
  * Remove mappings for a provided virtual address range

kernel/mmu.c

@@ -276,7 +276,6 @@ static void frame_mapped_set(struct z_page_frame *pf, void *addr)
  */
 static int map_anon_page(void *addr, uint32_t flags)
 {
-	int ret;
 	struct z_page_frame *pf;
 	uintptr_t phys;
 	bool lock = (flags & K_MEM_MAP_LOCK) != 0;
@@ -285,14 +284,10 @@ static int map_anon_page(void *addr, uint32_t flags)
 	if (pf == NULL) {
 		return -ENOMEM;
 	}
-	phys = z_page_frame_to_phys(pf);
 
-	ret = arch_mem_map(addr, phys, CONFIG_MMU_PAGE_SIZE,
+	phys = z_page_frame_to_phys(pf);
-			   flags | K_MEM_CACHE_WB);
+	arch_mem_map(addr, phys, CONFIG_MMU_PAGE_SIZE, flags | K_MEM_CACHE_WB);
-	if (ret != 0) {
+
-		free_page_frame_list_put(pf);
-		return -ENOMEM;
-	}
 	if (lock) {
 		pf->flags |= Z_PAGE_FRAME_PINNED;
 	}
@@ -385,7 +380,6 @@ void z_phys_map(uint8_t **virt_ptr, uintptr_t phys, size_t size, uint32_t flags)
 {
 	uintptr_t aligned_phys, addr_offset;
 	size_t aligned_size;
-	int ret;
 	k_spinlock_key_t key;
 	uint8_t *dest_addr;
 
@@ -413,11 +407,7 @@ void z_phys_map(uint8_t **virt_ptr, uintptr_t phys, size_t size, uint32_t flags)
 	LOG_DBG("arch_mem_map(%p, 0x%lx, %zu, %x) offset %lu", dest_addr,
 		aligned_phys, aligned_size, flags, addr_offset);
 
-	ret = arch_mem_map(dest_addr, aligned_phys, aligned_size, flags);
+	arch_mem_map(dest_addr, aligned_phys, aligned_size, flags);
-	if (ret != 0) {
-		LOG_ERR("arch_mem_map() failed with %d", ret);
-		goto fail;
-	}
 	k_spin_unlock(&z_mm_lock, key);
 
 	*virt_ptr = dest_addr + addr_offset;