From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756538Ab3BESNN (ORCPT ); Tue, 5 Feb 2013 13:13:13 -0500 Received: from mail-vc0-f173.google.com ([209.85.220.173]:45804 "EHLO mail-vc0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754070Ab3BESNK (ORCPT ); Tue, 5 Feb 2013 13:13:10 -0500 Date: Tue, 5 Feb 2013 13:13:06 -0500 (EST) From: Nicolas Pitre To: Rob Herring cc: Joonsoo Kim , Rob Herring , Russell King , js1304@gmail.com, Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v5 3/3] ARM: mm: use static_vm for managing static mapped areas In-Reply-To: <51114134.4070503@gmail.com> Message-ID: References: <1360024314-1895-1-git-send-email-iamjoonsoo.kim@lge.com> <1360024314-1895-4-git-send-email-iamjoonsoo.kim@lge.com> <51114134.4070503@gmail.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 5 Feb 2013, Rob Herring wrote: > On 02/04/2013 10:44 PM, Nicolas Pitre wrote: > > On Tue, 5 Feb 2013, Joonsoo Kim wrote: > > > >> A static mapped area is ARM-specific, so it is better not to use > >> generic vmalloc data structure, that is, vmlist and vmlist_lock > >> for managing static mapped area. And it causes some needless overhead and > >> reducing this overhead is better idea. > >> > >> Now, we have newly introduced static_vm infrastructure. > >> With it, we don't need to iterate all mapped areas. Instead, we just > >> iterate static mapped areas. It helps to reduce an overhead of finding > >> matched area. And architecture dependency on vmalloc layer is removed, > >> so it will help to maintainability for vmalloc layer. > >> > >> Signed-off-by: Joonsoo Kim > > [snip] > > >> @@ -859,17 +864,12 @@ static void __init pci_reserve_io(void) > >> { > >> struct vm_struct *vm; > >> unsigned long addr; > >> + struct static_vm *svm; > >> > >> - /* we're still single threaded hence no lock needed here */ > >> - for (vm = vmlist; vm; vm = vm->next) { > >> - if (!(vm->flags & VM_ARM_STATIC_MAPPING)) > >> - continue; > >> - addr = (unsigned long)vm->addr; > >> - addr &= ~(SZ_2M - 1); > >> - if (addr == PCI_IO_VIRT_BASE) > >> - return; > >> + svm = find_static_vm_vaddr((void *)PCI_IO_VIRT_BASE); > >> + if (svm) > >> + return; > >> > >> - } > >> > >> vm_reserve_area_early(PCI_IO_VIRT_BASE, SZ_2M, pci_reserve_io); > >> } > > > > The replacement code is not equivalent. I can't recall why the original > > is as it is, but it doesn't look right to me. The 2MB round down > > certainly looks suspicious. > > The PCI mapping is at a fixed, aligned 2MB mapping. If we find any > virtual address within that region already mapped, it is an error. Ah, OK. This wasn't clear looking at the code. > We probably should have had a WARN here. Indeed. > > > > The replacement code should be better. However I'd like you to get an > > ACK from Rob Herring as well for this patch. > > It doesn't appear to me the above case is handled. The virt addr is > checked whether it is within an existing mapping, but not whether the > new mapping would overlap an existing mapping. It would be good to check > for this generically rather than specifically for the PCI i/o mapping. Agreed. However that is checked already in vm_area_add_early(). Therefore the overlap test here is redundant. Nicolas