Message-ID: <431E2B23.40509@mvista.com>
Date: Tue, 06 Sep 2005 16:49:55 -0700
From: Mark Bellon <mbellon@mvista.com>
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To: Paul Mackerras <paulus@samba.org>
CC: linux-kernel@vger.kernel.org, linuxppc64-dev@ozlabs.org, akpm@osdl.org
Subject: Re: [PATCH]  PPC64: large INITRD causes kernel not to boot [UPDATE]
References: <431E1D1A.2090601@mvista.com> <17182.10581.159598.839256@cargo.ozlabs.ibm.com>
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Paul Mackerras wrote:

>Mark Bellon writes:
>
>  
>
>>Simply put the existing code has a fixed reservation (claim) address and 
>>once the kernel plus initrd image are large enough to pass this address 
>>all sorts of bad things occur. The fix is the dynamically establish the 
>>first claim address above the loaded kernel plus initrd (plus some 
>>"padding" and rounding). If PROG_START is defined this will be used as 
>>the minimum safe address - currently known to be 0x01400000 for the 
>>firmwares tested so far.
>>    
>>
>
>The idea is fine, but I have some questions about the actual patch:
>
>  
>
>>-void *claim(unsigned int, unsigned int, unsigned int);
>>+void *claim(unsigned long, unsigned long, unsigned long);
>>    
>>
>
>What was the motivation for this change?  Since the zImage wrapper is
>a 32-bit executable, int and long are both 32 bits.  I would prefer to
>leave the parameters as unsigned int to force people to realize that
>the parameters are 32 bits (even if said people have been working on
>64-bit programs recently).
>
>  
>
The function, claim, is found in prom.c uses longs. The long is the 
usual idiom for hiding a pointer, not an int, so I fixed accordingly. 
I'm open to further discussion of course.

On a 64 bit machine long and int are different sizes. This would make 
things "proper" if things changed in the future.

>>+	claim_base = _ALIGN_UP((unsigned long)_end, ONE_MB);
>>+
>>+#if defined(PROG_START)
>>+	/*
>>+	 * Maintain a "magic" minimum address. This keeps some older
>>+	 * firmware platforms running.
>>+	 */
>>+
>>+	if (claim_base < PROG_START)
>>+		claim_base = PROG_START;
>>+#endif
>>    
>>
>
>This appears to be the meat of the patch, the rest is "cleanup", right?
>  
>

Correct. The preceding comment explains what is going on. Removing the 
magic numbers seemed like a good idea.

mark

>Paul.
>  
>

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