From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yinghai Lu Subject: Re: [PATCH 28/31] memblock: Export MEMBLOCK_ERROR again Date: Tue, 27 Jul 2010 23:13:14 -0700 Message-ID: <4C4FCA7A.1020506@kernel.org> References: <1280294128.1970.237.camel@pasglop> <1280294376.1970.239.camel@pasglop> <4C4FC5D1.3070708@zytor.com> <20100727.230120.43037767.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from rcsinet10.oracle.com ([148.87.113.121]:24322 "EHLO rcsinet10.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752555Ab0G1GPT (ORCPT ); Wed, 28 Jul 2010 02:15:19 -0400 In-Reply-To: <20100727.230120.43037767.davem@davemloft.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: David Miller Cc: hpa@zytor.com, benh@kernel.crashing.org, mingo@elte.hu, tglx@linutronix.de, akpm@linux-foundation.org, torvalds@linux-foundation.org, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org On 07/27/2010 11:01 PM, David Miller wrote: > From: "H. Peter Anvin" > Date: Tue, 27 Jul 2010 22:53:21 -0700 > >> On 07/27/2010 10:19 PM, Benjamin Herrenschmidt wrote: >>> >>> Screw it, I don't like it but I'll just split your patch in two for now >>> and keep 0. It's a bit fishy but memblock does mostly top-down >>> allocations and so shouldn't hit 0, and in practice the region at 0 is, >>> I beleive, reserved, but we need to be extra careful and might need to >>> revisit that a bit. >>> >>> That's an area where I don't completely agree with Linus, ie, 0 is a >>> perfectly valid physical address for memblock to return :-) >>> >> >> On x86, physical address 0 contains the real-mode IVT and will thus be >> reserved, at least for the forseeable future. Other architectures may >> very well have non-special RAM there. > > 0 is very much possible on sparc64 So still keep MEMBLOCK_ERROR to (~(phys_addr_t)0) ? We can change some variable from unsigned long to phys_addr_t that will be assigned by memblock_find_base(). that could avoid casting too. Thanks Yinghai