util: Add a virtual memory allocator

This is simple linear-walk first-fit allocator roughly based on the
allocator in the radeon winsys code.  This allocator has two primary
functional differences:

 1) It cleanly returns 0 on allocation failure

 2) It allocates addresses top-down instead of bottom-up.

The second one is needed for Intel because high addresses (with bit 47
set) need to be canonicalized in order to work properly.  If we allocate
bottom-up, then high addresses will be very rare (if they ever happen).
We'd rather always have high addresses so that the canonicalization code
gets better testing.

v2: - [scott-ph] remove _heap_validate() if NDEBUG is defined (Jordan)

Reviewed-by: Scott D Phillips <scott.d.phillips@intel.com>
Tested-by: Scott D Phillips <scott.d.phillips@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/util/Makefile.sources

@@ -56,7 +56,9 @@ MESA_UTIL_FILES := \
 	u_string.h \
 	u_thread.h \
 	u_vector.c \
-	u_vector.h
+	u_vector.h \
+	vma.c \
+	vma.h
 
 MESA_UTIL_GENERATED_FILES = \
 	format_srgb.c

src/util/meson.build

@@ -81,6 +81,8 @@ files_mesa_util = files(
   'u_thread.h',
   'u_vector.c',
   'u_vector.h',
+  'vma.c',
+  'vma.h',
 )
 
 install_data('drirc', install_dir : get_option('sysconfdir'))

src/util/vma.c

@@ -0,0 +1,234 @@
+/*
+ * Copyright © 2018 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <stdlib.h>
+
+#include "util/u_math.h"
+#include "util/vma.h"
+
+struct util_vma_hole {
+   struct list_head link;
+   uint64_t offset;
+   uint64_t size;
+};
+
+#define util_vma_foreach_hole(_hole, _heap) \
+   list_for_each_entry(struct util_vma_hole, _hole, &(_heap)->holes, link)
+
+#define util_vma_foreach_hole_safe(_hole, _heap) \
+   list_for_each_entry_safe(struct util_vma_hole, _hole, &(_heap)->holes, link)
+
+void
+util_vma_heap_init(struct util_vma_heap *heap,
+                   uint64_t start, uint64_t size)
+{
+   list_inithead(&heap->holes);
+   util_vma_heap_free(heap, start, size);
+}
+
+void
+util_vma_heap_finish(struct util_vma_heap *heap)
+{
+   util_vma_foreach_hole_safe(hole, heap)
+      free(hole);
+}
+
+#ifndef NDEBUG
+static void
+util_vma_heap_validate(struct util_vma_heap *heap)
+{
+   uint64_t prev_offset = 0;
+   util_vma_foreach_hole(hole, heap) {
+      assert(hole->offset > 0);
+      assert(hole->size > 0);
+
+      if (&hole->link == heap->holes.next) {
+         /* This must be the top-most hole.  Assert that, if it overflows, it
+          * overflows to 0, i.e. 2^64.
+          */
+         assert(hole->size + hole->offset == 0 ||
+                hole->size + hole->offset > hole->offset);
+      } else {
+         /* This is not the top-most hole so it must not overflow and, in
+          * fact, must be strictly lower than the top-most hole.  If
+          * hole->size + hole->offset == prev_offset, then we failed to join
+          * holes during a util_vma_heap_free.
+          */
+         assert(hole->size + hole->offset > hole->offset &&
+                hole->size + hole->offset < prev_offset);
+      }
+      prev_offset = hole->offset;
+   }
+}
+#else
+#define util_vma_heap_validate(heap)
+#endif
+
+uint64_t
+util_vma_heap_alloc(struct util_vma_heap *heap,
+                    uint64_t size, uint64_t alignment)
+{
+   /* The caller is expected to reject zero-size allocations */
+   assert(size > 0);
+   assert(alignment > 0);
+
+   util_vma_heap_validate(heap);
+
+   util_vma_foreach_hole_safe(hole, heap) {
+      if (size > hole->size)
+         continue;
+
+      /* Compute the offset as the highest address where a chunk of the given
+       * size can be without going over the top of the hole.
+       *
+       * This calculation is known to not overflow because we know that
+       * hole->size + hole->offset can only overflow to 0 and size > 0.
+       */
+      uint64_t offset = (hole->size - size) + hole->offset;
+
+      /* Align the offset.  We align down and not up because we are allocating
+       * from the top of the hole and not the bottom.
+       */
+      offset = (offset / alignment) * alignment;
+
+      if (offset < hole->offset)
+         continue;
+
+      if (offset == hole->offset && size == hole->size) {
+         /* Just get rid of the hole. */
+         list_del(&hole->link);
+         free(hole);
+         util_vma_heap_validate(heap);
+         return offset;
+      }
+
+      assert(offset - hole->offset <= hole->size - size);
+      uint64_t waste = (hole->size - size) - (offset - hole->offset);
+      if (waste == 0) {
+         /* We allocated at the top.  Shrink the hole down. */
+         hole->size -= size;
+         util_vma_heap_validate(heap);
+         return offset;
+      }
+
+      if (offset == hole->offset) {
+         /* We allocated at the bottom. Shrink the hole up. */
+         hole->offset += size;
+         hole->size -= size;
+         util_vma_heap_validate(heap);
+         return offset;
+      }
+
+      /* We allocated in the middle.  We need to split the old hole into two
+       * holes, one high and one low.
+       */
+      struct util_vma_hole *high_hole = calloc(1, sizeof(*hole));
+      high_hole->offset = offset + size;
+      high_hole->size = waste;
+
+      /* Adjust the hole to be the amount of space left at he bottom of the
+       * original hole.
+       */
+      hole->size = offset - hole->offset;
+
+      /* Place the new hole before the old hole so that the list is in order
+       * from high to low.
+       */
+      list_addtail(&high_hole->link, &hole->link);
+
+      util_vma_heap_validate(heap);
+
+      return offset;
+   }
+
+   /* Failed to allocate */
+   return 0;
+}
+
+void
+util_vma_heap_free(struct util_vma_heap *heap,
+                   uint64_t offset, uint64_t size)
+{
+   /* An offset of 0 is reserved for allocation failure.  It is not a valid
+    * address and cannot be freed.
+    */
+   assert(offset > 0);
+
+   /* Freeing something with a size of 0 is also not valid. */
+   assert(size > 0);
+
+   /* It's possible for offset + size to wrap around if we touch the top of
+    * the 64-bit address space, but we cannot go any higher than 2^64.
+    */
+   assert(offset + size == 0 || offset + size > offset);
+
+   util_vma_heap_validate(heap);
+
+   /* Find immediately higher and lower holes if they exist. */
+   struct util_vma_hole *high_hole = NULL, *low_hole = NULL;
+   util_vma_foreach_hole(hole, heap) {
+      if (hole->offset <= offset) {
+         low_hole = hole;
+         break;
+      }
+      high_hole = hole;
+   }
+
+   if (high_hole)
+      assert(offset + size <= high_hole->offset);
+   bool high_adjacent = high_hole && offset + size == high_hole->offset;
+
+   if (low_hole) {
+      assert(low_hole->offset + low_hole->size > low_hole->offset);
+      assert(low_hole->offset + low_hole->size <= offset);
+   }
+   bool low_adjacent = low_hole && low_hole->offset + low_hole->size == offset;
+
+   if (low_adjacent && high_adjacent) {
+      /* Merge the two holes */
+      low_hole->size += size + high_hole->size;
+      list_del(&high_hole->link);
+      free(high_hole);
+   } else if (low_adjacent) {
+      /* Merge into the low hole */
+      low_hole->size += size;
+   } else if (high_adjacent) {
+      /* Merge into the high hole */
+      high_hole->offset = offset;
+      high_hole->size += size;
+   } else {
+      /* Neither hole is adjacent; make a new one */
+      struct util_vma_hole *hole = calloc(1, sizeof(*hole));
+
+      hole->offset = offset;
+      hole->size = size;
+
+      /* Add it after the high hole so we maintain high-to-low ordering */
+      if (high_hole)
+         list_add(&hole->link, &high_hole->link);
+      else
+         list_add(&hole->link, &heap->holes);
+   }
+
+   util_vma_heap_validate(heap);
+}

src/util/vma.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright © 2018 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#ifndef _UTIL_VMA_H
+#define _UTIL_VMA_H
+
+#include <stdint.h>
+
+#include "list.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct util_vma_heap {
+   struct list_head holes;
+};
+
+void util_vma_heap_init(struct util_vma_heap *heap,
+                        uint64_t start, uint64_t size);
+void util_vma_heap_finish(struct util_vma_heap *heap);
+
+uint64_t util_vma_heap_alloc(struct util_vma_heap *heap,
+                             uint64_t size, uint64_t alignment);
+
+void util_vma_heap_free(struct util_vma_heap *heap,
+                        uint64_t offset, uint64_t size);
+
+#ifdef __cplusplus
+} /* extern C */
+#endif
+
+#endif /* _UTIL_DEBUG_H */