[PATCH 3/3] xen: arm: rework dom0 initrd and dtb placement

[Ian Campbell <ian.campbell@citrix.com>]

This now uses the same decision tree as libxc (which is much easier to test).

The main change is to explictly handle the placement at 128MB or end of RAM as
two cases, rather than combining with MIN. The effect is the same but the code
is clearer.

Secondly the attempt to place the mopules right after the kernel is removed,
since it is redundant with the case where placing them at the end of RAM ends
up abutting the kernel.

Also round the kernel size up to a 2MB boundary.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
I'm sure to regret playing with this yet again...
---
 xen/arch/arm/kernel.c |   22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/xen/arch/arm/kernel.c b/xen/arch/arm/kernel.c
index bc625a4..1102392 100644
--- a/xen/arch/arm/kernel.c
+++ b/xen/arch/arm/kernel.c
@@ -77,7 +77,7 @@ static void place_modules(struct kernel_info *info,
     const paddr_t rambase = info->mem.bank[0].start;
     const paddr_t ramsize = info->mem.bank[0].size;
     const paddr_t ramend = rambase + ramsize;
-    const paddr_t kernsize = kernend - kernbase;
+    const paddr_t kernsize = ROUNDUP(kernend, MB(2)) - kernbase;
     const paddr_t ram128mb = rambase + MB(128);
 
     paddr_t modbase;
@@ -95,16 +95,18 @@ static void place_modules(struct kernel_info *info,
      * If the bootloader provides an initrd, it will be loaded just
      * after the DTB.
      *
-     * We try to place dtb+initrd at 128MB, (or, if we have less RAM,
-     * as high as possible). If there is no space then fallback to
-     * just after the kernel, if there is room, otherwise just before.
+     * We try to place dtb+initrd at 128MB or if we have less RAM
+     * as high as possible. If there is no space then fallback to
+     * just before the kernel.
+     *
+     * If changing this then consider
+     * tools/libxc/xc_dom_arm.c:arch_setup_meminit as well.
      */
-
-    if ( kernend < MIN(ram128mb, ramend - modsize) )
-        modbase = MIN(ram128mb, ramend - modsize);
-    else if ( ramend - ROUNDUP(kernend, MB(2)) >= modsize )
-        modbase = ROUNDUP(kernend, MB(2));
-    else if ( kernbase - rambase >= modsize )
+    if ( ramend >= ram128mb + modsize && kernend < ram128mb )
+        modbase = ram128mb;
+    else if ( ramend - modsize > ROUNDUP(kernend, MB(2)) )
+        modbase = ramend - modsize;
+    else if ( kernbase - rambase > modsize )
         modbase = kernbase - modsize;
     else
     {
-- 
1.7.10.4