Date: Sat, 23 Apr 2011 00:33:32 +0200
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
To: Daniel Kiper <dkiper@net-space.pl>
Cc: konrad.wilk@oracle.com, stefano.stabellini@eu.citrix.com,
        xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org
Subject: Re: [Xen-devel] [PATCH REPOST] pv-grub: Fix for incorrect dom->p2m_host[] list initialization
Message-ID: <20110422223331.GB5124@const.famille.thibault.fr>
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	Daniel Kiper <dkiper@net-space.pl>, konrad.wilk@oracle.com,
	stefano.stabellini@eu.citrix.com, xen-devel@lists.xensource.com,
	linux-kernel@vger.kernel.org
References: <20110422212545.GA22846@router-fw-old.local.net-space.pl>
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Hello,

Daniel Kiper, le Fri 22 Apr 2011 23:25:45 +0200, a ?crit :
> 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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