Re: [PATCH] ia64/mm: fix a bad_page bug when crash kernel booting

Matt Fleming
2013-02-04T16:32:45Z

On Tue, 2013-01-29 at 11:52 +0800, Xishi Qiu wrote:
> On ia64 platform, I set "crashkernel\x1024M-:600M", and dmesg shows 128M-728M
> memory is reserved for crash kernel. Then "echo c > /proc/sysrq-trigger" to
> test kdump.
>
> When crash kernel booting, efi_init() will aligns the memory address in
> IA64_GRANULE_SIZE(16M), so 720M-728M memory will be dropped, It means
> crash kernel only manage 128M-720M memory.
>
> But initrd start and end are fixed in boot loader, it is before efi_init(),
> so initrd size maybe overflow when free_initrd_mem().

[...]

> diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
> index b755ea9..cfdb1eb 100644
> --- a/arch/ia64/mm/init.c
> +++ b/arch/ia64/mm/init.c
> @@ -207,6 +207,17 @@ free_initrd_mem (unsigned long start, unsigned long end)
> start = PAGE_ALIGN(start);
> end = end & PAGE_MASK;
>
> + /*
> + * Initrd size is fixed in boot loader, but kernel parameter max_addr
> + * which aligns in granules is fixed after boot loader, so initrd size
> + * maybe overflow.
> + */
> + if (max_addr != ~0UL) {
> + end = GRANULEROUNDDOWN(end);
> + if (start > end)
> + start = end;
> + }
> +
> if (start < end)
> printk(KERN_INFO "Freeing initrd memory: %ldkB freed\n", (end - start) >> 10);

I don't think this is the correct fix.

Now, my ia64-fu is weak, but could it be that there's actually a bug in
efi_init() and that the following patch would be the best way to fix
this?

---

diff --git a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
index f034563..8d579f1 100644
--- a/arch/ia64/kernel/efi.c
+++ b/arch/ia64/kernel/efi.c
@@ -482,7 +482,7 @@ efi_init (void)
if (memcmp(cp, "mem=", 4) = 0) {
mem_limit = memparse(cp + 4, &cp);
} else if (memcmp(cp, "max_addr=", 9) = 0) {
- max_addr = GRANULEROUNDDOWN(memparse(cp + 9, &cp));
+ max_addr = GRANULEROUNDUP(memparse(cp + 9, &cp));
} else if (memcmp(cp, "min_addr=", 9) = 0) {
min_addr = GRANULEROUNDDOWN(memparse(cp + 9, &cp));
} else {