linux-kernel - Re: [PATCH kernel v8 03/31] vfio: powerpc/spapr: Check that IOMMU page is fully contained by system page

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Date:	Wed, 15 Apr 2015 14:03:25 +1000
From:	David Gibson <david@...son.dropbear.id.au>
To:	Alexey Kardashevskiy <aik@...abs.ru>
Cc:	linuxppc-dev@...ts.ozlabs.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH kernel v8 03/31] vfio: powerpc/spapr: Check that IOMMU
 page is fully contained by system page

On Fri, Apr 10, 2015 at 04:30:45PM +1000, Alexey Kardashevskiy wrote:
> This checks that the TCE table page size is not bigger that the size of
> a page we just pinned and going to put its physical address to the table.
> 
> Otherwise the hardware gets unwanted access to physical memory between
> the end of the actual page and the end of the aligned up TCE page.
> 
> Since compound_order() and compound_head() work correctly on non-huge
> pages, there is no need for additional check whether the page is huge.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>

Reviewed-by: David Gibson <david@...son.dropbear.id.au>

Only thing I'm not sure about is...

> +		if (!tce_page_is_contained(page, tbl->it_page_shift)) {
> +			ret = -EPERM;
> +			break;

.. whether EPERM is the right error code.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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