iommu/iova: Don't BUG on invalid PFNs

Unlike the other instances which represent a complete loss of
consistency within the rcache mechanism itself, or a fundamental
and obvious misconfiguration by an IOMMU driver, the BUG_ON() in
iova_magazine_free_pfns() can be provoked at more or less any time
in a "spooky action-at-a-distance" manner by any old device driver
passing nonsense to dma_unmap_*() which then propagates through to
queue_iova().

Not only is this well outside the IOVA layer's control, it's also
nowhere near fatal enough to justify panicking anyway - all that
really achieves is to make debugging the offending driver more
difficult. Let's simply WARN and otherwise ignore bogus PFNs.

Reported-by: Prakash Gupta <guptap@codeaurora.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Prakash Gupta <guptap@codeaurora.org>
Link: https://lore.kernel.org/r/acbd2d092b42738a03a21b417ce64e27f8c91c86.1591103298.git.robin.murphy@arm.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>
Change-Id: Ic8118863e89547ec03a3c0a96158aa38be8f41af
Git-Commit: d3e3d2be688b4b5864538de61e750721a311e4fc
Git-Repo: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git


Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>