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Re: [Xen-devel] 2.6.37 mainline kernel section mismatches

To: Arvind R <arvino55@xxxxxxxxx>
Subject: Re: [Xen-devel] 2.6.37 mainline kernel section mismatches
From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Date: Mon, 24 Jan 2011 11:40:28 +0000
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Sat, 22 Jan 2011, Arvind R wrote:
> Hi,
> Got 7 section mismatch warnings while compiling mainline 2.6.37 release 
> kernel.
> FILE                                   Caller Func
>       Callled Func      Warnings
> arch/x86/xen/enlighten.c    xen_hvm_init_shared_info    extend_brk          1
> arch/x86/xen/mmu.c           xen_build_mfn_list_list
> extend_brk          4
> Column 2 functions need __init qualifiers; but these functions are
> also called in
> non __init functions in suspend.c
> FILE                                   DATA
>          INITIALISER        Warnings
> drivers/xen/events.c           cpu_evtchn_mask_p
> &init_evtchn_mask    2
> Here init_evtchn_mask needs __initdata qualifier removed

the appended patch by Stefan Assmann should fix the issue, I'll try to
upstream it in the next merge window.


From: Stefan Assmann <sassmann@xxxxxxxxxx>

The following warning shows up when building the kernel with

WARNING: arch/x86/built-in.o(.text+0x475): Section mismatch in reference from 
the function xen_hvm_init_shared_info() to the function .init.text:extend_brk()
The function xen_hvm_init_shared_info() references
the function __init extend_brk().
This is often because xen_hvm_init_shared_info lacks a __init
annotation or the annotation of extend_brk is wrong.

The problem is that xen_hvm_init_shared_info() calls extend_brk() which is
an __init function. However xen_hvm_init_shared_info() cannot be an
__init function as it's called on system resume as well. Easy fix by
moving extend_brk() out of the function.

Signed-off-by: Stefan Assmann <sassmann@xxxxxxxxxx>
 arch/x86/xen/enlighten.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 02c710b..13b11fd 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -83,6 +83,7 @@ EXPORT_SYMBOL(machine_to_phys_order);
 struct start_info *xen_start_info;

+struct shared_info *shared_info_page;
 struct shared_info xen_dummy_shared_info;

 void *xen_initial_gdt;
@@ -1310,11 +1311,7 @@ void xen_hvm_init_shared_info(void)
        int cpu;
        struct xen_add_to_physmap xatp;
-       static struct shared_info *shared_info_page = 0;

-       if (!shared_info_page)
-               shared_info_page = (struct shared_info *)
-                       extend_brk(PAGE_SIZE, PAGE_SIZE);
        xatp.domid = DOMID_SELF;
        xatp.idx = 0;
        xatp.space = XENMAPSPACE_shared_info;
@@ -1365,6 +1362,9 @@ static void __init xen_hvm_guest_init(void)
        if (r < 0)

+       shared_info_page = (struct shared_info *)
+               extend_brk(PAGE_SIZE, PAGE_SIZE);

        if (xen_feature(XENFEAT_hvm_callback_vector))

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