[Xen-devel] Re: xen: do not create the extra e820 region at an addr lower than 4G

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

I can't find this patch on any mailing list to respond to so starting a
new thread. In case I've not missed it but instead it really wasn't
posted -- in the future can we try and ensure that any patches have been
posted at least once. Same for the pull request, it should go to a list.

BTW the version in Konrad's tree is Stefano's 2.6.39-rc1-fixes branch
but Stefano's tree only has 2.6.39-rc2-fixes now -- is that important?

Anyway, the patch itself:

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 9c38bd1..f831568 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -229,7 +229,7 @@ char * __init xen_memory_setup(void)
 
        memcpy(map_raw, map, sizeof(map));
        e820.nr_map = 0;
-       xen_extra_mem_start = mem_end;
+       xen_extra_mem_start = mem_end < (1UL<<32) ? (1UL<<32) : mem_end;
        for (i = 0; i < memmap.nr_entries; i++) {
                unsigned long long end;

"(1UL<<32)" will overflow on a 32 bit kernel.

Oh hang on... that's the difference between the -rc1 and -rc2 versions
of Stefano's branches:

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index f831568..ee44c56 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -229,7 +229,7 @@ char * __init xen_memory_setup(void)
 
        memcpy(map_raw, map, sizeof(map));
        e820.nr_map = 0;
-       xen_extra_mem_start = mem_end < (1UL<<32) ? (1UL<<32) : mem_end;
+       xen_extra_mem_start = max((1ULL <<32), mem_end);
        for (i = 0; i < memmap.nr_entries; i++) {
                unsigned long long end;

So I guess it was important!

(also the whitespace in "(1ULL <<32)" is a bit funky, checkpatch whinges
too)

Ian.


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