From mboxrd@z Thu Jan 1 00:00:00 1970 From: labbott@redhat.com (Laura Abbott) Date: Fri, 15 Jan 2016 15:03:42 -0800 Subject: [PATCH] staging: ion: make the pte default none PTE_RDONLY In-Reply-To: <1452825753-36364-1-git-send-email-puck.chen@hisilicon.com> References: <1452825753-36364-1-git-send-email-puck.chen@hisilicon.com> Message-ID: <56997ACE.80604@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org (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? Thanks, Laura