[PATCH 20/36] xen/common: introduce buddy required reservation

[Marco Solieri <marco.solieri@xxxxxxxxxxxxxxx>]

From: Luca Miccio <lucmiccio@xxxxxxxxx>

When cache coloring is enabled, a certain amount of memory is reserved
for buddy allocation because current coloring implementation does not
support Xen heap memory. As of this commit, the colored allocator is used
for dom0, domUs, while the buddy manages only Xen memory. The memory
reserved to the buddy is thus lowered to a reasonably small value.
Introduce a new variable that specifies the amount of memory reserved
for the buddy allocator.
The current default value will be enough even when we will add
coloring for Xen in the following patches.

Signed-off-by: Luca Miccio <lucmiccio@xxxxxxxxx>
Signed-off-by: Marco Solieri <marco.solieri@xxxxxxxxxxxxxxx>
---
 xen/common/page_alloc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 82f6e8330a..fffa438029 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -230,6 +230,13 @@ static bool __read_mostly scrub_debug;
 #define scrub_debug    false
 #endif
 
+#ifdef CONFIG_COLORING
+/* Minimum size required for buddy allocator to work with colored one */
+unsigned long buddy_required_size __read_mostly = MB(64);
+#else
+unsigned long buddy_required_size __read_mostly = 0;
+#endif
+
 /*
  * Bit width of the DMA heap -- used to override NUMA-node-first.
  * allocation strategy, which can otherwise exhaust low memory.
@@ -678,6 +685,13 @@ static void dump_col_heap(unsigned char key)
 
     printk("Total number of pages: %lu\n", total_avail_col_pages);
 }
+static int __init parse_buddy_required_size(const char *s)
+{
+    buddy_required_size = simple_strtoull(s, &s, 0);
+
+    return *s ? -EINVAL : 0;
+}
+custom_param("buddy_size", parse_buddy_required_size);
 #else /* !CONFIG_COLORING */
 #define init_col_heap_pages(x, y) init_heap_pages(x, y)
 
-- 
2.30.2