x86: mark page frame as reserved according to memory map

With x86, there are usually memory regions that are reserved
for firmware and device MMIOs. We don't want to use these
pages for memory mapping so mark them as reserved at boot.
The weakly defined x86_memmap contains the list of memory
regions which can be overriden by SoC or board configurations.
Also, with CONFIG_MULTIBOOT_MEMMAP=y, the memory regions
are populated from multiboot provided data.

Signed-off-by: Daniel Leung <[email protected]>

Author: dcpleung

arch/x86/core/x86_mmu.c

@@ -20,6 +20,7 @@
 #include <mmu.h>
 #include <drivers/interrupt_controller/loapic.h>
 #include <mmu.h>
+#include <arch/x86/memmap.h>
 
 LOG_MODULE_DECLARE(os, CONFIG_KERNEL_LOG_LEVEL);
 
@@ -1704,6 +1705,24 @@ void z_x86_current_stack_perms(void)
 #endif /* CONFIG_USERSPACE */
 
 #ifdef CONFIG_ARCH_HAS_RESERVED_PAGE_FRAMES
+static void mark_addr_page_reserved(uintptr_t addr, size_t len)
+{
+	uintptr_t pos = ROUND_DOWN(addr, CONFIG_MMU_PAGE_SIZE);
+	uintptr_t end = ROUND_UP(addr + len, CONFIG_MMU_PAGE_SIZE);
+
+	for (; pos < end; pos += CONFIG_MMU_PAGE_SIZE) {
+		if (!z_is_page_frame(pos)) {
+			continue;
+		}
+
+		struct z_page_frame *pf = z_phys_to_page_frame(pos);
+
+		pf->flags |= Z_PAGE_FRAME_RESERVED;
+
+		z_free_page_count--;
+	}
+}
+
 /* Selected on PC-like targets at the SOC level.
  *
  * Best is to do some E820 or similar enumeration to specifically identify
@@ -1713,11 +1732,28 @@ void z_x86_current_stack_perms(void)
  */
 void arch_reserved_pages_update(void)
 {
-	for (uintptr_t pos = 0; pos < (1024 * 1024);
-	     pos += CONFIG_MMU_PAGE_SIZE) {
-		struct z_page_frame *pf = z_phys_to_page_frame(pos);
+	mark_addr_page_reserved(0, MB(1));
 
-		pf->flags |= Z_PAGE_FRAME_RESERVED;
+	for (int i = 0; i < CONFIG_X86_MEMMAP_ENTRIES; i++) {
+		struct x86_memmap_entry *entry = &x86_memmap[i];
+
+		switch (entry->type) {
+		case X86_MEMMAP_ENTRY_UNUSED:
+			__fallthrough;
+		case X86_MEMMAP_ENTRY_RAM:
+			continue;
+
+		case X86_MEMMAP_ENTRY_ACPI:
+			__fallthrough;
+		case X86_MEMMAP_ENTRY_NVS:
+			__fallthrough;
+		case X86_MEMMAP_ENTRY_DEFECTIVE:
+			__fallthrough;
+		default:
+			break;
+		}
+
+		mark_addr_page_reserved(entry->base, entry->length);
 	}
 }
 #endif /* CONFIG_ARCH_HAS_RESERVED_PAGE_FRAMES */