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Re: [Xen-devel] [PATCH] libxc/arm: align to page size the base address of the device tree

On Tue, 2013-11-19 at 18:52 +0000, Julien Grall wrote:
> xc_dom_alloc_segment requires start address to be page align.

I wonder why I didn't see this? It seems very unlikely that my dtb would
be exactly page sized, yet it works... Ah, I have >128M of RAM in my
guest so the base would be 128M. Well spotted.

I think it would be slightly preferable to round dtbsize up to a page.
e.g. the following. What do you think?


From 079a2815d86567de1cbb541541d08a0b9ac3d18d Mon Sep 17 00:00:00 2001
From: Ian Campbell <ian.campbell@xxxxxxxxxx>
Date: Wed, 20 Nov 2013 09:45:32 +0000
Subject: [PATCH] libxl: arm: ensure DTB is page aligned

xc_dom_alloc_segment requires this. Since rambase and ramend are both page
aligned, rounding up the DTB is sufficient.

Reported-by: Julien Grall <julien.grall@xxxxxxxxxx>
Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
 tools/libxc/xc_dom_arm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/libxc/xc_dom_arm.c b/tools/libxc/xc_dom_arm.c
index ffe575b..a40e04d 100644
--- a/tools/libxc/xc_dom_arm.c
+++ b/tools/libxc/xc_dom_arm.c
@@ -282,7 +282,7 @@ int arch_setup_meminit(struct xc_dom_image *dom)
         const uint64_t rambase = dom->rambase_pfn << XC_PAGE_SHIFT;
         const uint64_t ramend = rambase + ( dom->total_pages << XC_PAGE_SHIFT 
-        const uint64_t dtbsize = ( dom->devicetree_size + 3 ) & ~0x3;
+        const uint64_t dtbsize = ROUNDUP(dom->devicetree_size, XC_PAGE_SHIFT);
         /* Place at 128MB if there is sufficient RAM */
         if ( ramend >= rambase + 128*1024*1024 + dtbsize )

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