pmm: simpler and bugfix process_memory_range loop

This simplifies the adding of frames during boot. It also fixes a bug for configurations with > 1GB memory. After the initial 4K frames, the current (`cur`) is aligned to 2MB. Trying to add a 1GB frame at this point will lead to page faults further down the line as we end up with misaligned page frame mfns. Signed-off-by: Johannes Wikner <[email protected]>
KernelTestFramework · Oct 31, 2024 · fa54601 · fa54601
1 parent c1ab591
commit fa54601
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Showing 3 changed files with 21 additions and 24 deletions.
diff --git a/include/arch/x86/page.h b/include/arch/x86/page.h
@@ -193,6 +193,7 @@ typedef unsigned long mfn_t;
 #define MAP_FAILED ((void *) 1)
 
 #define IS_ADDR_SPACE_VA(va, as) (_ul(va) >= (as))
+#define PADDR_TO_ORDER(addr)     (ctz(addr) - PAGE_SHIFT)
 
 /* External declarations */
 

diff --git a/include/compiler.h b/include/compiler.h
@@ -157,4 +157,6 @@ typedef uint64_t off_t;
         _str;                                                                            \
     })
 
+/* count trailing zeros */
+#define ctz __builtin_ctz
 #endif /* KTF_COMPILER_H */
diff --git a/mm/pmm.c b/mm/pmm.c
@@ -293,7 +293,6 @@ static unsigned find_first_avail_region(void) {
 
 static size_t process_memory_range(unsigned index, unsigned first_avail_region) {
     paddr_t start, end, cur;
-    unsigned int max_order;
     addr_range_t range;
     size_t size;
 
@@ -310,39 +309,34 @@ static size_t process_memory_range(unsigned index, unsigned first_avail_region)
      * because initial virtual memory mapping is small.
      */
 
-    /* Add initial 4K frames and align to 2M. */
-    while ((cur < MB(EARLY_VIRT_MEM) || cur % PAGE_SIZE_2M) && cur + PAGE_SIZE <= end) {
-        if (index <= first_avail_region)
-            add_early_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
-        else
-            add_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
+    /* Add initial 4K frames for early memory. */
+    while (cur < MB(EARLY_VIRT_MEM) && cur + PAGE_SIZE <= end) {
+        add_early_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
         cur += ORDER_TO_SIZE(PAGE_ORDER_4K);
     }
 
-    max_order = find_max_avail_order(end - cur);
-
-    /* Add all available max_order frames. */
-    while (cur + ORDER_TO_SIZE(max_order) <= end) {
-        add_frame(paddr_to_mfn(cur), max_order);
-        cur += ORDER_TO_SIZE(max_order);
-    }
+    while (cur + PAGE_SIZE <= end) {
+        unsigned int order = PADDR_TO_ORDER(cur);
+        if (order >= PAGE_ORDER_1G && cur + PAGE_SIZE_1G <= end) {
+            add_frame(paddr_to_mfn(cur), PAGE_ORDER_1G);
+            cur += ORDER_TO_SIZE(PAGE_ORDER_1G);
+            continue;
+        }
 
-    /* Add all remaining 2M frames. */
-    while (cur + PAGE_SIZE_2M <= end) {
-        add_frame(paddr_to_mfn(cur), PAGE_ORDER_2M);
-        cur += ORDER_TO_SIZE(PAGE_ORDER_2M);
-    }
+        if (order >= PAGE_ORDER_2M && cur + PAGE_SIZE_2M <= end) {
+            add_frame(paddr_to_mfn(cur), PAGE_ORDER_2M);
+            cur += ORDER_TO_SIZE(PAGE_ORDER_2M);
+            continue;
+        }
 
-    /* Add all remaining 4K frames. */
-    while (cur < end) {
         add_frame(paddr_to_mfn(cur), PAGE_ORDER_4K);
         cur += ORDER_TO_SIZE(PAGE_ORDER_4K);
     }
 
     if (cur != end) {
-        warning(
-            "PMM range processing failed: start=0x%016lx end=0x%016lx current=0x%016lx",
-            start, end, cur);
+        warning("PMM range processing failed: start=0x%016lx end=0x%016lx "
+                "current=0x%016lx",
+                start, end, cur);
     }
 
     return size;