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 <puck.chen@xxxxxxxxxxxxx> > >Signed-off-by: Wei Dong <weidong2@xxxxxxxxxxxxx> > >Reviewed-by: Zhuangluan Su <suzhuangluan@xxxxxxxxxxxxx> > >--- > > 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. _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
