[PATCH v3] biosmem: Narrow e820 regions as required

[Damien Zammit]

---
 i386/i386at/biosmem.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/i386/i386at/biosmem.c b/i386/i386at/biosmem.c
index 4f0914ca..78e7bb21 100644
--- a/i386/i386at/biosmem.c
+++ b/i386/i386at/biosmem.c
@@ -82,6 +82,19 @@ static unsigned int biosmem_nr_boot_data __bootdata;
 #define BIOSMEM_TYPE_UNUSABLE   5
 #define BIOSMEM_TYPE_DISABLED   6

+/*
+ * Bitmask corresponding to memory ranges that require narrowing
+ * to page boundaries.
+ */
+#define BIOSMEM_MASK_NARROW    (((1u << BIOSMEM_TYPE_AVAILABLE) | \
+                                 (1u << BIOSMEM_TYPE_NVS) | \
+                                 (1u << BIOSMEM_TYPE_DISABLED)))
+
+/*
+ * Helper macro to test if range type needs narrowing.
+ */
+#define BIOSMEM_NEEDS_NARROW(t)        ((1u << t) & BIOSMEM_MASK_NARROW)
+
 /*
  * Memory map entry.
  */
@@ -248,6 +261,17 @@ biosmem_unregister_boot_data(phys_addr_t start, 
phys_addr_t end)

 #ifndef MACH_HYP

+static void __boot
+biosmem_map_adjust_alignment(struct biosmem_map_entry *e)
+{
+    uint64_t end = e->base_addr + e->length;
+
+    if (BIOSMEM_NEEDS_NARROW(e->type)) {
+        e->base_addr = vm_page_round (e->base_addr);
+        e->length = vm_page_trunc (end) - e->base_addr;
+    }
+}
+
 static void __boot
 biosmem_map_build(const struct multiboot_raw_info *mbi)
 {
@@ -268,6 +292,8 @@ biosmem_map_build(const struct multiboot_raw_info *mbi)
         entry->type = mb_entry->type;

         mb_entry = (void *)mb_entry + sizeof(mb_entry->size) + mb_entry->size;
+
+        biosmem_map_adjust_alignment(entry);
         entry++;
     }

@@ -283,11 +309,13 @@ biosmem_map_build_simple(const struct multiboot_raw_info 
*mbi)
     entry->base_addr = 0;
     entry->length = mbi->mem_lower << 10;
     entry->type = BIOSMEM_TYPE_AVAILABLE;
+    biosmem_map_adjust_alignment(entry);

     entry++;
     entry->base_addr = BIOSMEM_END;
     entry->length = mbi->mem_upper << 10;
     entry->type = BIOSMEM_TYPE_AVAILABLE;
+    biosmem_map_adjust_alignment(entry);

     biosmem_map_size = 2;
 }
--
2.34.1