From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932725Ab2GEMhw (ORCPT ); Thu, 5 Jul 2012 08:37:52 -0400 Received: from mail-vb0-f46.google.com ([209.85.212.46]:45764 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932699Ab2GEMhr (ORCPT ); Thu, 5 Jul 2012 08:37:47 -0400 MIME-Version: 1.0 In-Reply-To: <1341412376-6272-1-git-send-email-will.deacon@arm.com> References: <1341412376-6272-1-git-send-email-will.deacon@arm.com> Date: Thu, 5 Jul 2012 20:37:46 +0800 Message-ID: Subject: Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace From: Hillf Danton To: Will Deacon Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.cz, linux-kernel@vger.kernel.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 On Wed, Jul 4, 2012 at 10:32 PM, Will Deacon wrote: > When allocating and returning clear huge pages to userspace as a > response to a fault, we may zero and return a mapping to a previously > dirtied physical region (for example, it may have been written by > a private mapping which was freed as a result of an ftruncate on the > backing file). On architectures with Harvard caches, this can lead to > I/D inconsistency since the zeroed view may not be visible to the > instruction stream. > > This patch solves the problem by flushing the region after allocating > and clearing a new huge page. Note that PowerPC avoids this issue by > performing the flushing in their clear_user_page implementation to keep > the loader happy, however this is closely tied to the semantics of the > PG_arch_1 page flag which is architecture-specific. > > Acked-by: Catalin Marinas > Signed-off-by: Will Deacon > --- Thanks:) Acked-by: Hillf Danton > mm/hugetlb.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index e198831..b83d026 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2646,6 +2646,7 @@ retry: > goto out; > } > clear_huge_page(page, address, pages_per_huge_page(h)); > + flush_dcache_page(page); > __SetPageUptodate(page); > > if (vma->vm_flags & VM_MAYSHARE) { > -- > 1.7.4.1 > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx113.postini.com [74.125.245.113]) by kanga.kvack.org (Postfix) with SMTP id 2F5706B0074 for ; Thu, 5 Jul 2012 08:37:48 -0400 (EDT) Received: by vcbfl10 with SMTP id fl10so6747356vcb.14 for ; Thu, 05 Jul 2012 05:37:47 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1341412376-6272-1-git-send-email-will.deacon@arm.com> References: <1341412376-6272-1-git-send-email-will.deacon@arm.com> Date: Thu, 5 Jul 2012 20:37:46 +0800 Message-ID: Subject: Re: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace From: Hillf Danton Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Will Deacon Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.cz, linux-kernel@vger.kernel.org On Wed, Jul 4, 2012 at 10:32 PM, Will Deacon wrote: > When allocating and returning clear huge pages to userspace as a > response to a fault, we may zero and return a mapping to a previously > dirtied physical region (for example, it may have been written by > a private mapping which was freed as a result of an ftruncate on the > backing file). On architectures with Harvard caches, this can lead to > I/D inconsistency since the zeroed view may not be visible to the > instruction stream. > > This patch solves the problem by flushing the region after allocating > and clearing a new huge page. Note that PowerPC avoids this issue by > performing the flushing in their clear_user_page implementation to keep > the loader happy, however this is closely tied to the semantics of the > PG_arch_1 page flag which is architecture-specific. > > Acked-by: Catalin Marinas > Signed-off-by: Will Deacon > --- Thanks:) Acked-by: Hillf Danton > mm/hugetlb.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index e198831..b83d026 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2646,6 +2646,7 @@ retry: > goto out; > } > clear_huge_page(page, address, pages_per_huge_page(h)); > + flush_dcache_page(page); > __SetPageUptodate(page); > > if (vma->vm_flags & VM_MAYSHARE) { > -- > 1.7.4.1 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org