linux-kernel - Re: [Xen-devel] [PATCH REPOST] pv-grub: Fix for incorrect dom->p2m

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Message-ID: <20110422223331.GB5124@const.famille.thibault.fr>
Date:	Sat, 23 Apr 2011 00:33:32 +0200
From:	Samuel Thibault <samuel.thibault@...-lyon.org>
To:	Daniel Kiper <dkiper@...-space.pl>
Cc:	konrad.wilk@...cle.com, stefano.stabellini@...citrix.com,
	xen-devel@...ts.xensource.com, linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH REPOST] pv-grub: Fix for incorrect dom->p2m_host[] list initialization

Hello,

Daniel Kiper, le Fri 22 Apr 2011 23:25:45 +0200, a écrit :
> If pfn of newly allocated page is less than currently requested pfn
> then relevant earlier allocated mfn is overwritten which leads to
> domain crash later.

Oops, good catch! And unfortunately it happens seldomly... I guess it
may be the culprit for a fair number of other issues.

> +	if (new_pfn < i)
> +		for (new_pfn = i; new_pfn < dom->total_pages; ++new_pfn)
> +			if (dom->p2m_host[new_pfn] == new_mfn)
> +				break;

Instead of looking for the page, which takes a linear time for each page
and thus potentially quadratic time, we should probably rather record
which PFN the MFNs < allocated have been moved to?

Samuel
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