mini-os: add description of x86 memory usage

Add a brief description how the physical and virtual address usage
looks like on x86 to include/x86/arch_mm.h

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

diff --git a/include/x86/arch_mm.h b/include/x86/arch_mm.h
index 58f29fcfaad80c47e1a1515662a19ea2042491b3..f756dabba89eeac86d090ee4110d4b0b3bf19e48 100644 (file)
--- a/include/x86/arch_mm.h
+++ b/include/x86/arch_mm.h
@@ -36,6 +36,26 @@
 #endif
 #endif
 
+/*
+ * Physical address space usage:
+ *
+ * 0..._edata: kernel text/data
+ * *stack    : kernel stack (thread 0)
+ * hypervisor allocated data: p2m_list, start_info page, xenstore page,
+ *                            console page, initial page tables
+ * bitmap of allocated pages
+ * pages controlled by the page allocator
+ *
+ *
+ * Virtual address space usage:
+ *
+ * 1:1 mapping of physical memory starting at VA(0)
+ * 1 unallocated page
+ * demand map area (32 bits: 2 GB, 64 bits: 128 GB) for virtual allocations
+ * 1 unallocated page
+ * with libc: heap area (32 bits: 1 GB, 64 bits: 128 GB)
+ */
+
 #define L1_FRAME                1
 #define L2_FRAME                2
 #define L3_FRAME                3