pr51254_54395.uvm_map.c.diff

Index: uvm_map.c
===================================================================
RCS file: /cvsroot/src/sys/uvm/uvm_map.c,v
retrieving revision 1.401
diff -p -u -r1.401 uvm_map.c
--- uvm_map.c	6 Jun 2022 07:00:02 -0000	1.401
+++ uvm_map.c	6 Jun 2022 07:04:27 -0000
@@ -199,6 +199,53 @@ uvm_map_align_va(vaddr_t *vap, vsize_t a
 }
 
 /*
+ * uvm_map_adjust_va: adjust va according to constraints and PMAP_PREFER
+ */
+static void
+uvm_map_adjust_va(vaddr_t *vap, vsize_t length, voff_t uoffset, vsize_t align,
+    int flags, int topdown)
+{
+
+#ifdef PMAP_PREFER
+	/*
+	 * push va forward as needed to avoid VAC alias problems.
+	 * we only do this if a valid offset is specified.
+	 */
+
+	if (uoffset != UVM_UNKNOWN_OFFSET)
+		PMAP_PREFER(uoffset, vap, length, topdown);
+#endif
+	if ((flags & UVM_FLAG_COLORMATCH) != 0) {
+		KASSERT(align < uvmexp.ncolors);
+		if (uvmexp.ncolors > 1) {
+			const u_int colormask = uvmexp.colormask;
+			const u_int colorsize = colormask + 1;
+			vaddr_t hint = atop(*vap);
+			const u_int color = hint & colormask;
+			if (color != align) {
+				hint -= color;	/* adjust to color boundary */
+				KASSERT((hint & colormask) == 0);
+				if (topdown) {
+					if (align > color)
+						hint -= colorsize;
+				} else {
+					if (align < color)
+						hint += colorsize;
+				}
+				*vap = ptoa(hint + align); /* adjust to color */
+			}
+		}
+	} else {
+		KASSERT(powerof2(align));
+		uvm_map_align_va(vap, align, topdown);
+		/*
+		 * XXX Should we PMAP_PREFER() here again?
+		 * eh...i think we're okay
+		 */
+	}
+}
+
+/*
  * UVM_ET_ISCOMPATIBLE: check some requirements for map entry merging
  */
 extern struct vm_map *pager_map;
@@ -1724,43 +1771,11 @@ uvm_map_space_avail(vaddr_t *start, vsiz
 {
 	vaddr_t end;
 
-#ifdef PMAP_PREFER
 	/*
-	 * push start address forward as needed to avoid VAC alias problems.
-	 * we only do this if a valid offset is specified.
+	 * First, adjust start according to constraints and PMAP_PREFER.
 	 */
 
-	if (uoffset != UVM_UNKNOWN_OFFSET)
-		PMAP_PREFER(uoffset, start, length, topdown);
-#endif
-	if ((flags & UVM_FLAG_COLORMATCH) != 0) {
-		KASSERT(align < uvmexp.ncolors);
-		if (uvmexp.ncolors > 1) {
-			const u_int colormask = uvmexp.colormask;
-			const u_int colorsize = colormask + 1;
-			vaddr_t hint = atop(*start);
-			const u_int color = hint & colormask;
-			if (color != align) {
-				hint -= color;	/* adjust to color boundary */
-				KASSERT((hint & colormask) == 0);
-				if (topdown) {
-					if (align > color)
-						hint -= colorsize;
-				} else {
-					if (align < color)
-						hint += colorsize;
-				}
-				*start = ptoa(hint + align); /* adjust to color */
-			}
-		}
-	} else {
-		KASSERT(powerof2(align));
-		uvm_map_align_va(start, align, topdown);
-		/*
-		 * XXX Should we PMAP_PREFER() here again?
-		 * eh...i think we're okay
-		 */
-	}
+	uvm_map_adjust_va(start, length, uoffset, align, flags, topdown);
 
 	/*
 	 * Find the end of the proposed new region.  Be sure we didn't
@@ -1870,11 +1885,15 @@ uvm_map_findspace(struct vm_map *map, va
 	    hint, vm_map_min(map), vm_map_max(map), 0);
 
 	/*
-	 * hint may not be aligned properly; we need round up or down it
-	 * before proceeding further.
+	 * hint may not satisfy constraints and PMAP_PREFER; we need
+	 * round up or down it before proceeding further. Otherwise,
+	 * we end up with inconsistencies; see kern/51254 and 54395.
+	 *
+	 * XXX UVM_FLAG_FIXED is superior to PMAP_PREFER?
 	 */
-	if ((flags & UVM_FLAG_COLORMATCH) == 0) {
-		uvm_map_align_va(&hint, align, topdown);
+	if ((flags & UVM_FLAG_FIXED) == 0) {
+		uvm_map_adjust_va(&hint, length, uoffset, align, flags,
+		    topdown);
 		INVARIANTS();
 	}