On Fri, Aug 04, 2023 at 01:04:57PM +0000, Liu, Yi L wrote: > > > Having the driver copy in a loop might be better > > > > > > > Can you elaborate? > > I think Jason means the way in patch 09. Yeah, you can't reuse the stack buffer for an array, so patch 9 copies each element uniquely. This is more calls to copy_to_user, which has some cost But we avoid a memory allocation Patch 9 should not abuse the user_data, cast it to the inv_info and just put req on the stack: struct iommu_hwpt_vtd_s1_invalidate *inv_info = user_data; struct iommu_hwpt_vtd_s1_invalidate_desc req; But I'm not sure about this entry_size logic, what happens if the entry_size is larger than the kernel supports? I think it should fail.. Jason
