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Date: Thu, 20 Nov 2003 09:01:50 -0800
To: "Randy.Dunlap" <rddunlap@osdl.org>
Cc: linux-kernel@vger.kernel.org, dwmw2@infradead.org
Subject: Re: [PATCH/RFC] Re: Crash-on-boot in init_l440gx SMP
Message-ID: <20031120170150.GA21782@perens.com>
References: <20031030200203.159BD321@workstation.perens.com> <20031031114849.3e2c5425.rddunlap@osdl.org>
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From: bruce@perens.com (Bruce Perens)
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Randy,

I ran this patch on my main server for two weeks. Just yesterday we had
one kernel hang that I have no reason to believe is related to the patch,
especially since it took two weeks to come up. We have had no other problems
related to the kernel in that time.

Regarding the hang, it appears that disk I/O was blocked. I hit
Ctrl-Alt-SysRequest-s, and it started working again. I'm sorry to have
no other information on that.

	Thanks

	Bruce

On Fri, Oct 31, 2003 at 11:48:49AM -0800, Randy.Dunlap wrote:
> On Thu, 30 Oct 2003 12:02:03 -0800 (PST) bruce@perens.com (Bruce Perens) wrote:
> 
> | Hi,
> | 
> | Using -test9, I'm hitting BUG_ON(phys_addr + size < phys_addr) in ioremap.c,
> | called from init_l440gx with a dual Pentum 3 SMP motherboard. Boot log with
> | oops, and ksymoops output are attached. This system is main server for
> | perens.com, and thus hasn't exercised 2.6 much. Please email me if I can be
> | of any further assistance.
> | 
> | ------------[ cut here ]------------
> | kernel BUG at arch/i386/mm/ioremap.c:202!
> | invalid operand: 0000 [#1]
> | CPU:    0
> | EIP:    0060:[<c011e778>]    Not tainted
> | EFLAGS: 00010207
> | EIP is at ioremap_nocache+0xb8/0xd0
> | eax: c37fd800   ebx: cc000000   ecx: 00000000   edx: 00000100
> | esi: cc814000   edi: 00100000   ebp: fff00000   esp: cbfc1f84
> | ds: 007b   es: 007b   ss: 0068
> | Process swapper (pid: 1, threadinfo=cbfc0000 task=c11ff900)
> | Stack: fff00000 00100000 00000010 c37fd800 00007113 cbf23000 cbf23c00 00000000 
> |        c040b465 fff00000 00100000 00000000 00000000 c04145f0 c04145f4 00000001 
> |        00000000 c03f29ab 00000000 00000000 c013739f 00000000 cbfc0000 c01050f6 
> | Call Trace:
> |  [<c040b465>] init_l440gx+0x65/0x290
> |  [<c03f29ab>] do_initcalls+0x2b/0xa0
> |  [<c013739f>] init_workqueues+0xf/0x24
> |  [<c01050f6>] init+0x56/0x180
> |  [<c01050a0>] init+0x0/0x180
> |  [<c01092b9>] kernel_thread_helper+0x5/0xc
> | 
> | Code: 0f 0b ca 00 f8 db 33 c0 eb af 0f 0b c9 00 f8 db 33 c0 eb a1 
> |  <0>Kernel panic: Attempted to kill init!
> 
> drivers/mtd/maps/l440gx.c:
> 
> 	l440gx_map.virt = (unsigned long)ioremap_nocache(WINDOW_ADDR, WINDOW_SIZE);
> 
> where WINDOW_ADDR + WINDOW_SIZE == 0 (i.e., wraps to 0).
> 
> 
> I can see why it would be a problem to wrap around and above 0,
> but is it a problem to wrap exactly to 0?  I.e., to use the very
> top of the address space?
> 
> Is the patch below sufficient for this case, or does it need
> to call change_page_attr() also?
> 
> --
> ~Randy
> 
> 
> description:	allow ioremap_nocache() to reach to the very top of
> 		physical memory (i.e., allow the wrapped address to be 0)
> product_versions: Linux 2.6.0-test9
> patch_name:	ioremap-wrap.patch
> author:		Randy.Dunlap <rddunlap@osdl.org>
> patch_version:	2003-10-31.11:36:14
> 
> diffstat:=
>  arch/i386/mm/ioremap.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff -Naurp ./arch/i386/mm/ioremap.c~ioremap-wrap ./arch/i386/mm/ioremap.c
> --- ./arch/i386/mm/ioremap.c~ioremap-wrap	2003-10-25 11:43:13.000000000 -0700
> +++ ./arch/i386/mm/ioremap.c	2003-10-31 11:27:32.000000000 -0800
> @@ -191,15 +191,18 @@ void * __ioremap(unsigned long phys_addr
>  void *ioremap_nocache (unsigned long phys_addr, unsigned long size)
>  {
>  	void *p = __ioremap(phys_addr, size, _PAGE_PCD);
> +	unsigned long next_addr;
> +
>  	if (!p) 
>  		return p; 
>  
> -	if (phys_addr + size < virt_to_phys(high_memory)) { 
> +	next_addr = phys_addr + size;
> +	if (next_addr != 0 && next_addr < virt_to_phys(high_memory)) { 
>  		struct page *ppage = virt_to_page(__va(phys_addr));		
>  		unsigned long npages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
>  
> -		BUG_ON(phys_addr+size > (unsigned long)high_memory);
> -		BUG_ON(phys_addr + size < phys_addr);
> +		BUG_ON(next_addr > (unsigned long)high_memory);
> +		BUG_ON(next_addr < phys_addr);
>  
>  		if (change_page_attr(ppage, npages, PAGE_KERNEL_NOCACHE) < 0) { 
>  			iounmap(p);