From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751258AbcAOXYO (ORCPT ); Fri, 15 Jan 2016 18:24:14 -0500 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:42074 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750802AbcAOXYN (ORCPT ); Fri, 15 Jan 2016 18:24:13 -0500 Date: Fri, 15 Jan 2016 23:23:34 +0000 From: Russell King - ARM Linux To: Laura Abbott Cc: Chen Feng , gregkh@linuxfoundation.org, arve@android.com, riandrews@android.com, paul.gortmaker@windriver.com, gioh.kim@lge.com, tranmanphong@gmail.com, mitchelh@codeaurora.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, yudongbin@hisilicon.com, saberlily.xia@hisilicon.com, suzhuangluan@hisilicon.com, kong.kongxinwei@hisilicon.com, xuyiping@hisilicon.com, z.liuxinliang@hisilicon.com, weidong2@hisilicon.com, w.f@huawei.com, puck.chen@foxmail.com, shimingxing@hisilicon.com, oliver.fu@hisilicon.com, albert.lubing@hisilicon.com, chenxiang9@huawei.com, liuzixing@huawei.com, haojian.zhuang@linaro.org, Catalin Marinas , Will Deacon , dan.zhao@hisilicon.com, peter.panshilin@hisilicon.com, linuxarm@huawei.com, dev@lists.96boards.org, qijiwen@hisilicon.com, linux-arm-kernel Subject: Re: [PATCH] staging: ion: make the pte default none PTE_RDONLY Message-ID: <20160115232334.GD19062@n2100.arm.linux.org.uk> References: <1452825753-36364-1-git-send-email-puck.chen@hisilicon.com> <56997ACE.80604@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56997ACE.80604@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 15, 2016 at 03:03:42PM -0800, Laura Abbott wrote: > (adding linux-arm and a few people) > > On 01/14/2016 06:42 PM, Chen Feng wrote: > >The page is already alloc at ion_alloc function, > >ion_mmap map the alloced pages to user-space. > > > >The default prot can be PTE_RDONLY. Take a look at > >here: > >set_pte_at() > >arch/arm64/include/asm: > > if (pte_dirty(pte) && pte_write(pte)) > > pte_val(pte) &= ~PTE_RDONLY; > > else > > pte_val(pte) |= PTE_RDONLY; > > > >So with the dirty bit,it can improve the efficiency > >and donnot need to handle memory fault when use access. > > > >Signed-off-by: Chen Feng > >Signed-off-by: Wei Dong > >Reviewed-by: Zhuangluan Su > >--- > > drivers/staging/android/ion/ion.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > >diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c > >index e237e9f..dba5942 100644 > >--- a/drivers/staging/android/ion/ion.c > >+++ b/drivers/staging/android/ion/ion.c > >@@ -1026,6 +1026,9 @@ static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) > > if (!(buffer->flags & ION_FLAG_CACHED)) > > vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot); > > > >+ /*Default writeable*/ > >+ vma->vm_page_prot = pte_mkdirty(vma->vm_page_prot); > >+ > > mutex_lock(&buffer->lock); > > /* now map it to userspace */ > > ret = buffer->heap->ops->map_user(buffer->heap, buffer, vma); > > > > The extra fault is unfortunate but I'm skeptical about just setting > pte_mkdirty. > > Catalin/Will, do you have any thoughts? Right now it seems like any > range mapped with remap_pfn_range will have this extra fault > behavior. Is marking the range dirty the best solution? What happens if the mapping requested was read only - at the very least, I don't think this should be done unconditionally. -- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.