From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Subject: Re: [PATCH 2/5] swiotlb: Add is_swiotlb_active() function
Date: Thu, 24 Jan 2019 09:41:07 +0100
Message-ID: <20190124084107.GA19441@lst.de>
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To: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
Cc: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>, jon.grimm-5C7GfCeVMHo@public.gmane.org, brijesh.singh-5C7GfCeVMHo@public.gmane.org, Konrad Rzeszutek Wilk <konrad.wilk-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, Jason Wang <jasowang-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, "Michael S . Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, jfehlig-IBi9RG/b67k@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, jroedel-l3A5Bk7waGM@public.gmane.org, Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
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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.