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Message-ID: <17182.10581.159598.839256@cargo.ozlabs.ibm.com>
Date: Wed, 7 Sep 2005 09:42:13 +1000
From: Paul Mackerras <paulus@samba.org>
To: Mark Bellon <mbellon@mvista.com>
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]
In-Reply-To: <431E1D1A.2090601@mvista.com>
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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).

> +	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?

Paul.
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