Re: [PATCH 2/5] swiotlb: Add is_swiotlb_active() function

From: Christoph Hellwig
Date: Thu Jan 24 2019 - 03:41:11 EST

On Thu, Jan 24, 2019 at 09:29:23AM +0100, Joerg Roedel wrote:
> > As I've just introduced and fixed a bug in this area in the current
> > cycle - I don't think no_iotlb_memory is what your want (and maybe
> > not useful at all): if the arch valls swiotlb_exit after previously
> > initializing a buffer it won't be set. You probably want to check
> > for non-zero io_tlb_start and/or io_tlb_end.
> Okay, but that requires that I also set io_tlb_start and friends back to
> zero in the failure path of swiotlb_init(). Otherwise it could be left
> non-zero in case swiotlb_init_with_tbl() returns an error.

Indeed, and we'll need to do that anyway as otherwise the dma mapping
path might cause problems similar to the one when swiotlb_exit is
called that I fixed.