(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? Thanks, Laura _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
