linux-kernel - Re: [PATCH] iommu/amd: Only unmap large pages from the first pte

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Message-ID: <20130623120020.GB2557@8bytes.org>
Date:	Sun, 23 Jun 2013 14:00:25 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/amd: Only unmap large pages from the first pte

On Fri, Jun 21, 2013 at 02:33:19PM -0600, Alex Williamson wrote:
> If we use a large mapping, the expectation is that only unmaps from
> the first pte in the superpage are supported.  Unmaps from offsets
> into the superpage should fail (ie. return zero sized unmap).  In the
> current code, unmapping from an offset clears the size of the full
> mapping starting from an offset.  For instance, if we map a 16k
> physically contiguous range at IOVA 0x0 with a large page, then
> attempt to unmap 4k at offset 12k, 4 ptes are cleared (12k - 28k) and
> the unmap returns 16k unmapped.  This potentially incorrectly clears
> valid mappings and confuses drivers like VFIO that use the unmap size
> to release pinned pages.
> 
> Fix by refusing to unmap from offsets into the page.
> 
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> Cc: stable@...r.kernel.org

Applied, thanks for fixing this.


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