From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH v9 03/16] iommu/exynos: fix page table maintenance
Date: Wed, 14 Aug 2013 12:49:38 +0200
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To: Grant Grundler <grundler-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux Samsung SOC <linux-samsung-soc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Prathyush <prathyush.k-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>, Sachin Kamat <sachin.kamat-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Tomasz Figa <t.figa-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>, Subash Patel <supash.ramaswamy-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Linux Kernel <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Linux IOMMU <iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Kukjin Kim <kgene.kim-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>, Antonios Motakis <a.motakis-lrHrjnjw1UfHK3s98zE1ajGjJy/sRE9J@public.gmane.org>, Cho KyongHo <pullip.cho-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>, kvmarm-FPEHb7Xf0XXUo1n7N8X6UoWGPAHP3yOg@public.gmane.org, Linux ARM Kernel <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, Rahul Sharma <rahul.sharma-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>
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On Thu, Aug 08, 2013 at 11:28:44AM -0700, Grant Grundler wrote:
> I can't speak to the previous BUG_ON(). I believe the EADDRESSINUSE
> failures could be either WARN_ON or BUG_ON.   This condition is
> clearly a bug in the generic IOMMU allocator and I think that's why
> KyongHo Cho used BUG_ON.
> 
> Handing out duplicate addresses will generally lead to some sort of
> data corruption or other fault depending on how robust the underlying
> device drivers are written.  So my preference is a BUG_ON to
> immediately flag this condition instead of hoping a device driver will
> correctly handling the dma mapping failure (Some do, most currently
> don't).
> 
> WARN_ON() + return -EADDRESSINUSE would be a good alternative.

Even if it is a real BUG condition, I don't think it is worth to stop
execution at this point. It makes debugging harder and the system less
reliable. I prefer to go with the WARN_ON and an error return value.


	Joerg