From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753805Ab2GDOdQ (ORCPT ); Wed, 4 Jul 2012 10:33:16 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:48809 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752628Ab2GDOdP (ORCPT ); Wed, 4 Jul 2012 10:33:15 -0400 From: Will Deacon To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, dhillf@gmail.com, mhocko@suse.cz, linux-kernel@vger.kernel.org, Will Deacon Subject: [PATCH] mm: hugetlb: flush dcache before returning zeroed huge page to userspace Date: Wed, 4 Jul 2012 15:32:56 +0100 Message-Id: <1341412376-6272-1-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 1.7.4.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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