boot, pmm: add compile-time configurable early address space

Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
KernelTestFramework · Aug 17, 2021 · 83de1e2 · 83de1e2
1 parent 7bda5b3
commit 83de1e2
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Showing 4 changed files with 46 additions and 26 deletions.
diff --git a/.config b/.config
@@ -1 +1,3 @@
+# Size (in MB) of boot-time virtual address space coverage
+CONFIG_EARLY_VIRT_MEM=8
 CONFIG_LIBPFM=n
diff --git a/Makefile b/Makefile
@@ -76,7 +76,7 @@ ifeq ($(CONFIG_LIBPFM),y)
 COMMON_INCLUDES += -I$(PFMLIB_INCLUDE)
 endif
 
-COMMON_FLAGS := $(COMMON_INCLUDES) -pipe -MP -MMD -m64 -D__x86_64__
+COMMON_FLAGS := $(COMMON_INCLUDES) -pipe -MP -MMD -m64 -D__x86_64__ -DEARLY_VIRT_MEM=$(CONFIG_EARLY_VIRT_MEM)
 
 ifeq ($(CONFIG_LIBPFM),y)
 COMMON_FLAGS += -DKTF_PMU

diff --git a/arch/x86/boot/pagetables.S b/arch/x86/boot/pagetables.S
@@ -26,41 +26,52 @@
 #include <asm-macros.h>
 #include <page.h>
 
-/* Initial identity map page tables */
-SECTION(.data.init, "aw", PAGE_SIZE)
+#define EARLY_PT_NUM (EARLY_VIRT_MEM / 2)
+#define PT_NAME(x) l1_pt_entries ## x
+
+#if EARLY_PT_NUM > L2_PT_ENTRIES
+#error "Unable to cover more than 1GB of early address space"
+#endif
+
+#define FIRST_PT_IDX 0
 
 /* Each single l1_pt_entry covers a 4K of virtual addr range */
+.macro alloc_l1_pt idx
+    GLOBAL(PT_NAME(\idx))
+        .rept L1_PT_ENTRIES
+        .long PT_PADDR(PT_NAME(0), L1_PT_SHIFT) + L1_PROT, 0
+        .endr
+    END_OBJECT(PT_NAME(\idx))
+.endm
 
-/* First 2M range 0-2M */
-GLOBAL(l1_pt_entries1)
-    .rept L1_PT_ENTRIES
-    .long PT_PADDR(l1_pt_entries1, L1_PT_SHIFT) + L1_PROT, 0
-    .endr
-END_OBJECT(l1_pt_entries1)
+.macro l2_pt_entry idx
+    .long PT_NAME(\idx) + L2_PROT, 0
+.endm
 
-/* Second 2M range 2M-4M */
-GLOBAL(l1_pt_entries2)
-    .rept L1_PT_ENTRIES
-    .long PT_PADDR(l1_pt_entries1, L1_PT_SHIFT) + L1_PROT, 0
-    .endr
-END_OBJECT(l1_pt_entries2)
+.altmacro
 
-/* Third 2M range 4M-6M */
-GLOBAL(l1_pt_entries3)
-    .rept L1_PT_ENTRIES
-    .long PT_PADDR(l1_pt_entries1, L1_PT_SHIFT) + L1_PROT, 0
-    .endr
-END_OBJECT(l1_pt_entries3)
+/* Initial identity map page tables */
+SECTION(.data.init, "aw", PAGE_SIZE)
+
+/* Allocate L1 page tables */
+.set i, FIRST_PT_IDX
+.rept EARLY_PT_NUM
+    alloc_l1_pt %i
+    .set i, i + 1
+.endr
 
 /* 
  * Each single l2_pt_entry points to l1_pt_entry table and 
  * thus a single l2_pt_entry covers a 2M of virtual addr range 
  */
 GLOBAL(l2_pt_entries)
-    .long l1_pt_entries1 + L2_PROT, 0           /* Covers 0-2M */
-    .long l1_pt_entries2 + L2_PROT, 0           /* Covers 2M-4M */
-    .long l1_pt_entries3 + L2_PROT, 0           /* Covers 4M-6M */
-    .fill (L2_PT_ENTRIES - 3), PTE_SIZE, 0      /* 3 entries used, rests all are zeroed */
+    /* Assign L1 page tables to their L2 table */
+    .set i, FIRST_PT_IDX
+    .rept EARLY_PT_NUM
+        l2_pt_entry %i
+        .set i, i + 1
+    .endr
+    .fill (L2_PT_ENTRIES - EARLY_PT_NUM), PTE_SIZE, 0      /* EARLY_PT_NUM entries used, rests all are zeroed */
 END_OBJECT(l2_pt_entries)
 
 /* 
@@ -99,3 +110,5 @@ GLOBAL(l4_pt_entries)
     .long l3_pt_entries + L4_PROT, 0
 END_OBJECT(l4_pt_entries)
 #endif
+
+.noaltmacro
diff --git a/mm/pmm.c b/mm/pmm.c
@@ -99,7 +99,7 @@ static size_t process_memory_range(unsigned index) {
      */
 
     /* Add initial 4K frames and align to 2M. */
-    while (cur % PAGE_SIZE_2M && cur + PAGE_SIZE <= end) {
+    while ((cur < MB(EARLY_VIRT_MEM) || cur % PAGE_SIZE_2M) && cur + PAGE_SIZE <= end) {
         if (index <= 1)
             add_early_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
         else
@@ -169,6 +169,11 @@ void init_pmm(void) {
         total_phys_memory += process_memory_range(i);
 
     display_frames_count();
+
+    if (frames_count[PAGE_ORDER_4K] < (MB(EARLY_VIRT_MEM) / PAGE_SIZE))
+        panic("Not enough early frames: %u missing\n",
+              (MB(EARLY_VIRT_MEM) / PAGE_SIZE) - frames_count[PAGE_ORDER_4K]);
+
     if (opt_debug)
         display_frames();
 }