kexec on mips

kexec on mips

[Nikolai Zhubr]

Hello all,

I'm running both openwrt and debian on a mips-based wndr3800 netgear 
router/ap and I'm using kexec to arrange kind of dual-boot in a safe and 
comfortable manner.

Now, I've found that the following is critical for kexec to actually work:
--- arch/mips/kernel/machine_kexec.c.orig       2012-02-08 
01:58:13.000000000 +0300
+++ arch/mips/kernel/machine_kexec.c    2012-02-20 22:19:11.000000000 +0300
@@ -52,7 +52,7 @@
         reboot_code_buffer =
           (unsigned long)page_address(image->control_code_page);

-       kexec_start_address = image->start;
+       kexec_start_address = (unsigned long) phys_to_virt(image->start);
         kexec_indirection_page =
                 (unsigned long) phys_to_virt(image->head & PAGE_MASK);

I've found that in openwrt repository this change was present (among 
others) in a big patchset targeted for kernel 2.6.30 and now it is still 
present as a small separate patch for 2.6.38 
(target/linux/generic/patches-2.6.38/303-mips_fix_kexec.patch) and maybe 
others. Meanwhile, the latest _stable_ openwrt for the moment (backfire 
10.03.1) was released with kernel 2.6.32 without this patch so I had to 
dig through some forums to find the reason of kexec not working 
out-of-the-box. I've just now checked and the latest kernel.org's stable 
kernel (3.2.6) does not seem to include this either. Ok, since I know 
the secret already I'll fix it for myself anytime, but maybe some kind 
soul could just submit this _one_ line upstream? I'd say this feature is 
really handy in some cases.

Thank you.

(Please CC me, I'm not subscribed to linux-mips)

Nikolai