Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935007Ab3E2CPl (ORCPT ); Tue, 28 May 2013 22:15:41 -0400 Received: from mail-wg0-f48.google.com ([74.125.82.48]:47678 "EHLO mail-wg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934981Ab3E2CPk (ORCPT ); Tue, 28 May 2013 22:15:40 -0400 MIME-Version: 1.0 In-Reply-To: <51A4FC08.3060906@ti.com> References: <1369738100-11152-1-git-send-email-ratbert.chuang@gmail.com> <20130528130502.GA28971@mudshark.cambridge.arm.com> <51A4B938.7080708@ti.com> <20130528140705.GE28971@mudshark.cambridge.arm.com> <51A4FC08.3060906@ti.com> From: Po-Yu Chuang Date: Wed, 29 May 2013 10:14:58 +0800 Message-ID: Subject: Re: [PATCH] ARM: map_init_section flushes incorrect pmd To: Sricharan R Cc: Will Deacon , "linux@arm.linux.org.uk" , "nico@linaro.org" , Catalin Marinas , "linux-kernel@vger.kernel.org" , "rob.herring@calxeda.com" , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2882 Lines: 72 On Wed, May 29, 2013 at 2:48 AM, Sricharan R wrote: > > On Tuesday 28 May 2013 07:37 PM, Will Deacon wrote: > > On Tue, May 28, 2013 at 03:03:36PM +0100, Sricharan R wrote: > >> On Tuesday 28 May 2013 06:35 PM, Will Deacon wrote: > >>> On Tue, May 28, 2013 at 11:48:20AM +0100, Po-Yu Chuang wrote: > >>>> This bug was introduced in commit e651eab0. > >>>> Some v4/v5 platforms failed to boot due to this. > >>>> > >>>> Signed-off-by: Po-Yu Chuang > >>>> --- > >>>> arch/arm/mm/mmu.c | 4 +++- > >>>> 1 file changed, 3 insertions(+), 1 deletion(-) > >>>> > >>>> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c > >>>> index e0d8565..19a43f8 100644 > >>>> --- a/arch/arm/mm/mmu.c > >>>> +++ b/arch/arm/mm/mmu.c > >>>> @@ -620,6 +620,8 @@ static void __init map_init_section(pmd_t *pmd, unsigned long addr, > >>>> unsigned long end, phys_addr_t phys, > >>>> const struct mem_type *type) > >>>> { > >>>> + pmd_t *p = pmd; > >>>> + > >>>> #ifndef CONFIG_ARM_LPAE > >>>> /* > >>>> * In classic MMU format, puds and pmds are folded in to > >>>> @@ -638,7 +640,7 @@ static void __init map_init_section(pmd_t *pmd, unsigned long addr, > >>>> phys += SECTION_SIZE; > >>>> } while (pmd++, addr += SECTION_SIZE, addr != end); > >>>> > >>>> - flush_pmd_entry(pmd); > >>>> + flush_pmd_entry(p); > >>> Wait, shouldn't this flush be *inside* the loop anyway? Otherwise we just > >>> flush the cacheline containing the first pmd. The flushing code could also > >>> flush to PoU instead of PoC for UP ARMv7, but that's an unrelated optimisation. > >> I think in LPAE this loop iterates once and non LPAE twice. > >> So both the entries should be contained in same cache line right ? > > Dunno, are there any guarantees about alignment of the starting pmd? Even > > so, the function takes the range as parameters, so I don't think we > > should tailor it to the caller. It may explain why this hasn't come up > > sooner though. > > > > Will > > This function is not exposed outside. And the ranges passed to this is going > to not more than 2 entries in any case. If we put the flush inside the loop, > then we will end up doing an extra flush for the same line. Regarding the > alignment, I think if the pgd base is aligned, then rest should be fine. > Will have to check this. > > Regards, > Sricharan > Hi , Catalin and Sricharan, Thanks for your explanation. Will, I guess nobody noticed this because the MMU of later v7 processors fetches page table from D-cache. It even doesn't need to clean pmd to PoU. Regards, Po-Yu -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/