[RFC PATCH v2 12/48] lmb: allow for resizing lmb regions

Sughosh Ganu sughosh.ganu at linaro.org
Thu Jul 4 09:35:08 CEST 2024


Allow for resizing of LMB regions if the region attributes match. The
current code returns a failure status on detecting an overlapping
address. This worked up until now since the LMB calls were not
persistent and global -- the LMB memory map was specific and private
to a given caller of the LMB API's.

With the change in the LMB code to make the LMB reservations
persistent, there needs to be a check on whether the memory region can
be resized, and then do it if so. To distinguish between memory that
cannot be resized, add a new flag, LMB_NOOVERWRITE. Reserving a region
of memory with this attribute would indicate that the region cannot be
resized.

Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
---
Changes since V1:
* Do the check for the region flags in lmb_resize_regions() and
  lmb_merge_overlap_regions() to decide on merging the overlapping
  regions.

 include/lmb.h |   1 +
 lib/lmb.c     | 116 ++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 103 insertions(+), 14 deletions(-)

diff --git a/include/lmb.h b/include/lmb.h
index 069c6af2a3..99fcf5781f 100644
--- a/include/lmb.h
+++ b/include/lmb.h
@@ -20,6 +20,7 @@
 enum lmb_flags {
 	LMB_NONE		= 0x0,
 	LMB_NOMAP		= 0x4,
+	LMB_NOOVERWRITE		= 0x8,
 };
 
 /**
diff --git a/lib/lmb.c b/lib/lmb.c
index 0d01e58a46..80945e3cae 100644
--- a/lib/lmb.c
+++ b/lib/lmb.c
@@ -230,12 +230,88 @@ void lmb_init_and_reserve_range(phys_addr_t base, phys_size_t size,
 	lmb_reserve_common(fdt_blob);
 }
 
+static bool lmb_region_flags_match(struct lmb_region *rgn, unsigned long r1,
+				   enum lmb_flags flags)
+{
+	return rgn->region[r1].flags == flags;
+}
+
+static long lmb_merge_overlap_regions(struct lmb_region *rgn, unsigned long i,
+				      phys_addr_t base, phys_size_t size,
+				      enum lmb_flags flags)
+{
+	phys_size_t rgnsize;
+	unsigned long rgn_cnt, idx;
+	phys_addr_t rgnbase, rgnend;
+	phys_addr_t mergebase, mergeend;
+
+	rgn_cnt = 0;
+	idx = i;
+	/*
+	 * First thing to do is to identify how many regions does
+	 * the requested region overlap.
+	 * If the flags match, combine all these overlapping
+	 * regions into a single region, and remove the merged
+	 * regions.
+	 */
+	while (idx < rgn->cnt - 1) {
+		rgnbase = rgn->region[idx].base;
+		rgnsize = rgn->region[idx].size;
+
+		if (lmb_addrs_overlap(base, size, rgnbase,
+				      rgnsize)) {
+			if (!lmb_region_flags_match(rgn, idx, flags))
+				return -1;
+			rgn_cnt++;
+			idx++;
+		}
+	}
+
+	/* The merged region's base and size */
+	rgnbase = rgn->region[i].base;
+	mergebase = min(base, rgnbase);
+	rgnend = rgn->region[idx].base + rgn->region[idx].size;
+	mergeend = max(rgnend, (base + size));
+
+	rgn->region[i].base = mergebase;
+	rgn->region[i].size = mergeend - mergebase;
+
+	/* Now remove the merged regions */
+	while (--rgn_cnt)
+		lmb_remove_region(rgn, i + 1);
+
+	return 0;
+}
+
+static long lmb_resize_regions(struct lmb_region *rgn, unsigned long i,
+			       phys_addr_t base, phys_size_t size,
+			       enum lmb_flags flags)
+{
+	long ret = 0;
+	phys_addr_t rgnend;
+
+	if (i == rgn->cnt - 1 ||
+		base + size < rgn->region[i + 1].base) {
+		if (!lmb_region_flags_match(rgn, i, flags))
+			return -1;
+
+		rgnend = rgn->region[i].base + rgn->region[i].size;
+		rgn->region[i].base = min(base, rgn->region[i].base);
+		rgnend = max(base + size, rgnend);
+		rgn->region[i].size = rgnend - rgn->region[i].base;
+	} else {
+		ret = lmb_merge_overlap_regions(rgn, i, base, size, flags);
+	}
+
+	return ret;
+}
+
 /* This routine called with relocation disabled. */
 static long lmb_add_region_flags(struct lmb_region *rgn, phys_addr_t base,
 				 phys_size_t size, enum lmb_flags flags)
 {
 	unsigned long coalesced = 0;
-	long adjacent, i;
+	long ret, i;
 
 	if (rgn->cnt == 0) {
 		rgn->region[0].base = base;
@@ -260,23 +336,28 @@ static long lmb_add_region_flags(struct lmb_region *rgn, phys_addr_t base,
 				return -1; /* regions with new flags */
 		}
 
-		adjacent = lmb_addrs_adjacent(base, size, rgnbase, rgnsize);
-		if (adjacent > 0) {
+		ret = lmb_addrs_adjacent(base, size, rgnbase, rgnsize);
+		if (ret > 0) {
 			if (flags != rgnflags)
 				break;
 			rgn->region[i].base -= size;
 			rgn->region[i].size += size;
 			coalesced++;
 			break;
-		} else if (adjacent < 0) {
+		} else if (ret < 0) {
 			if (flags != rgnflags)
 				break;
 			rgn->region[i].size += size;
 			coalesced++;
 			break;
 		} else if (lmb_addrs_overlap(base, size, rgnbase, rgnsize)) {
-			/* regions overlap */
-			return -1;
+			ret = lmb_resize_regions(rgn, i, base, size,
+						 flags);
+			if (ret < 0)
+				return -1;
+
+			coalesced++;
+			break;
 		}
 	}
 
@@ -418,7 +499,7 @@ static phys_addr_t lmb_align_down(phys_addr_t addr, phys_size_t size)
 }
 
 static phys_addr_t __lmb_alloc_base(phys_size_t size, ulong align,
-				    phys_addr_t max_addr)
+				    phys_addr_t max_addr, enum lmb_flags flags)
 {
 	long i, rgn;
 	phys_addr_t base = 0;
@@ -468,7 +549,7 @@ phys_addr_t lmb_alloc_base(phys_size_t size, ulong align, phys_addr_t max_addr)
 {
 	phys_addr_t alloc;
 
-	alloc = __lmb_alloc_base(size, align, max_addr);
+	alloc = __lmb_alloc_base(size, align, max_addr, LMB_NONE);
 
 	if (alloc == 0)
 		printf("ERROR: Failed to allocate 0x%lx bytes below 0x%lx.\n",
@@ -477,11 +558,8 @@ phys_addr_t lmb_alloc_base(phys_size_t size, ulong align, phys_addr_t max_addr)
 	return alloc;
 }
 
-/*
- * Try to allocate a specific address range: must be in defined memory but not
- * reserved
- */
-phys_addr_t lmb_alloc_addr(phys_addr_t base, phys_size_t size)
+static phys_addr_t __lmb_alloc_addr(phys_addr_t base, phys_size_t size,
+				    enum lmb_flags flags)
 {
 	long rgn;
 
@@ -496,13 +574,23 @@ phys_addr_t lmb_alloc_addr(phys_addr_t base, phys_size_t size)
 				      lmb->memory.region[rgn].size,
 				      base + size - 1, 1)) {
 			/* ok, reserve the memory */
-			if (lmb_reserve(base, size) >= 0)
+			if (lmb_reserve_flags(base, size, flags) >= 0)
 				return base;
 		}
 	}
+
 	return 0;
 }
 
+/*
+ * Try to allocate a specific address range: must be in defined memory but not
+ * reserved
+ */
+phys_addr_t lmb_alloc_addr(phys_addr_t base, phys_size_t size)
+{
+	return __lmb_alloc_addr(base, size, LMB_NONE);
+}
+
 /* Return number of bytes from a given address that are free */
 phys_size_t lmb_get_free_size(phys_addr_t addr)
 {
-- 
2.34.1



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