From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756672AbYHGWKg (ORCPT ); Thu, 7 Aug 2008 18:10:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753259AbYHGWK1 (ORCPT ); Thu, 7 Aug 2008 18:10:27 -0400 Received: from gw.goop.org ([64.81.55.164]:45757 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753068AbYHGWK0 (ORCPT ); Thu, 7 Aug 2008 18:10:26 -0400 Message-ID: <489B72C3.30603@goop.org> Date: Thu, 07 Aug 2008 15:10:11 -0700 From: Jeremy Fitzhardinge User-Agent: Thunderbird 2.0.0.14 (X11/20080501) MIME-Version: 1.0 To: Andrew Morton CC: ehabkost@redhat.com, x86@kernel.org, Linux Kernel Mailing List Subject: Re: [PATCH] Make PFN_PHYS return a properly-formed physical address References: <489B6B40.5050705@goop.org> <20080807145648.ab3dfa90.akpm@linux-foundation.org> In-Reply-To: <20080807145648.ab3dfa90.akpm@linux-foundation.org> X-Enigmail-Version: 0.95.6 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andrew Morton wrote: > On Thu, 07 Aug 2008 14:38:08 -0700 > Jeremy Fitzhardinge wrote: > > >> PFN_PHYS, as its name suggests, turns a pfn into a physical address. >> However, it is a macro which just operates on its argument without >> modifying its type. pfns are typed unsigned long, but an unsigned >> long may not be long enough to hold a physical address (32-bit systems >> with more than 32 bits of physcial address). This means that the >> resulting address could be truncated if it doesn't fit within an >> unsigned long. This isn't generally a problem because most users end >> up using it for "low" memory, but there's no reason why PFN_PHYS >> couldn't be used for any possible pfn. >> > > Please copy a mailing list on patches. So you can get your titties > toasted off ;) > Oops. Forgot. >> Fortunately, resource_size_t is the right size, and has approximately >> the right meaning. It's 64-bits on platforms where that's >> appropriate, but 32-bits where the extra bits are not needed. >> > > aww maaan. Hack or what? > I don't know. Is it? It's what linux/ioport.h:struct resource uses to hold "start" and "end", which presumably means its intended to hold arbitrary physical addresses. >> #define PFN_ALIGN(x) (((unsigned long)(x) + (PAGE_SIZE - 1)) & PAGE_MASK) >> #define PFN_UP(x) (((x) + PAGE_SIZE-1) >> PAGE_SHIFT) >> #define PFN_DOWN(x) ((x) >> PAGE_SHIFT) >> -#define PFN_PHYS(x) ((x) << PAGE_SHIFT) >> +#define PFN_PHYS(x) ((resource_size_t)(x) << PAGE_SHIFT) >> > > Busted on PAE with CONFIG_RESOURCES_64BIT=n, surely? > Not an option: config X86_PAE def_bool n prompt "PAE (Physical Address Extension) Support" depends on X86_32 && !HIGHMEM4G select RESOURCES_64BIT And if you don't enable RESOURCES_64BIT, then I guess it's reasonable for PFN_PHYS to discount the possibility of high pages? > Can we please do this properly, whatever that is? Even a dumb > always-return-u64 would be better? > I had that originally, but someone (hpa?) suggested resource_size_t. The sad thing is that most users don't really care; they're either 64-bit anyway, or immediately truncate the result to 32-bit. "Properly" would be to define a phys_addr_t which can always represent a physical address. We have one in x86-land, but I hesitate to add it for everyone else. >> printk("initrd extends beyond end of memory " >> - "(0x%08lx > 0x%08lx)\ndisabling initrd\n", >> + "(0x%08lx > 0x%08llx)\ndisabling initrd\n", >> INITRD_START + INITRD_SIZE, >> PFN_PHYS(max_low_pfn)); >> > > that'll generate a compile warning if m32r can set CONFIG_RESOURCES_64BIT=n. > (u64) cast, I guess. J