linux-kernel - Re: [RFC 0/3] iommu/iova: Unsafe locking in find

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Message-ID: <20180706151321.sq25kc7otgjo3xvn@8bytes.org>
Date:   Fri, 6 Jul 2018 17:13:21 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org,
        David Woodhouse <dwmw2@...radead.org>,
        iommu@...ts.linux-foundation.org,
        Dmitry Safonov <0x7f454c46@...il.com>
Subject: Re: [RFC 0/3] iommu/iova: Unsafe locking in find_iova()

On Fri, Jul 06, 2018 at 03:10:47PM +0100, Dmitry Safonov wrote:
> Yes, as far as I can see, there are code-paths which may try to handle
> it at the same time:
> o memory notifiers for hot-unplug (intel-iommu.c)
> o drivers unloading calls free_iova(), which in the result calls
>   find_iova()
> o I see at least one driver that frees iova during it's normal work
>   too: scif_rma.c:scif_free_window_offset()

Yeah, but the IOVAs freed in the memory notifiers are just the ones for
the direct-mapped RMRR regions requested by firmware, not the IOVAs
allocated by any driver, so I think this shouldn't be a problem.


Regards,

	Joerg