linux-kernel - Re: [PATCH] kernel parameter vmalloc size fix

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Message-ID: <a8e1da0806160108x3de46eafp545275eb9dfd4f98@mail.gmail.com>
Date:	Mon, 16 Jun 2008 16:08:59 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, hpa@...or.com,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH] kernel parameter vmalloc size fix

On Mon, Jun 16, 2008 at 4:01 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Dave Young <hidave.darkstar@...il.com> wrote:
>
>> booting kernel with vmalloc=[any size<=16m] will oops.
>>
>> It's due to the vm area hole.
>>
>> In include/asm-x86/pgtable_32.h:
>> #define VMALLOC_OFFSET        (8 * 1024 * 1024)
>> #define VMALLOC_START (((unsigned long)high_memory + 2 * VMALLOC_OFFSET - 1) \
>>                        & ~(VMALLOC_OFFSET - 1))
>>
>> BUG_ON in arch/x86/mm/init_32.c will be triggered:
>> BUG_ON((unsigned long)high_memory             > VMALLOC_START);
>>
>> Fixed by return -EINVAL for invalid parameter
>
> hm. Why dont we instead add the size of the hole to the
> __VMALLOC_RESERVE value instead? There's nothing inherently bad about
> using vmalloc=16m. The VM area hole is really a kernel-internal
> abstraction that should not be visible in the usage of the parameter.

Good suggestion, thanks. I will rewrite the patch and send.

-- 
Regards
dave
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