Xen devel - May 2011 - [PATCH] arch/x86/xen/setup: Fix for incorrect xen_extra_mem_start initialization ifdef CONFIG_X86_32

git commit 24bdb0b62cc82120924762ae6bc85afc8c3f2b26 (xen: do not create
the extra e820 region at an addr lower than 4G) does not take into
account that ifdef CONFIG_X86_32 instead of e820_end_of_low_ram_pfn()
find_low_pfn_range() is called (both calls are from arch/x86/kernel/setup.c).
find_low_pfn_range() behaves correctly and does not require change in
xen_extra_mem_start initialization. Additionally, if xen_extra_mem_start
is initialized in the same way as ifdef CONFIG_X86_64 then memory hotplug
support for Xen balloon driver (under development) is broken.

Signed-off-by: Daniel Kiper <dkiper@net-space.pl>
---
 arch/x86/xen/setup.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 90bac0a..721f576 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -227,7 +227,11 @@ char * __init xen_memory_setup(void)
 
 	memcpy(map_raw, map, sizeof(map));
 	e820.nr_map = 0;
+#ifdef CONFIG_X86_32
+	xen_extra_mem_start = mem_end;
+#else
 	xen_extra_mem_start = max((1ULL << 32), mem_end);
+#endif
 	for (i = 0; i < memmap.nr_entries; i++) {
 		unsigned long long end;
 
-- 
1.5.6.5

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On Wed, May 11, 2011 at 10:34:38PM +0200, Daniel Kiper
wrote:
> git commit 24bdb0b62cc82120924762ae6bc85afc8c3f2b26 (xen: do not create
> the extra e820 region at an addr lower than 4G) does not take into
> account that ifdef CONFIG_X86_32 instead of e820_end_of_low_ram_pfn()
> find_low_pfn_range() is called (both calls are from
arch/x86/kernel/setup.c).
> find_low_pfn_range() behaves correctly and does not require change in
> xen_extra_mem_start initialization. Additionally, if xen_extra_mem_start
> is initialized in the same way as ifdef CONFIG_X86_64 then memory hotplug
> support for Xen balloon driver (under development) is broken.
in linux-next.

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On Thu, May 12, 2011 at 02:58:08PM -0400, Konrad Rzeszutek Wilk
wrote:
> On Wed, May 11, 2011 at 10:34:38PM +0200, Daniel Kiper wrote:
> > git commit 24bdb0b62cc82120924762ae6bc85afc8c3f2b26 (xen: do not
create
> > the extra e820 region at an addr lower than 4G) does not take into
> > account that ifdef CONFIG_X86_32 instead of e820_end_of_low_ram_pfn()
> > find_low_pfn_range() is called (both calls are from
arch/x86/kernel/setup.c).
> > find_low_pfn_range() behaves correctly and does not require change in
> > xen_extra_mem_start initialization. Additionally, if
xen_extra_mem_start
> > is initialized in the same way as ifdef CONFIG_X86_64 then memory
hotplug
> > support for Xen balloon driver (under development) is broken.
>
> in linux-next.
Thanks. Additionally, I would like to mention that git commit
279b706bf800b5967037f492dbe4fc5081ad5d0f
(x86,xen: introduce x86_init.mapping.pagetable_reserve) which fixes bug
introduced by
git commit 4b239f458c229de044d6905c2b0f9fe16ed9e01e (x86-64, mm: Put early page
table
high) works on my machine.

Daniel

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