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xen-devel
[Xen-devel] Re: [PATCH V2] pv-grub: Fix for incorrect dom->p2m_host[] li
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To: |
Daniel Kiper <dkiper@xxxxxxxxxxxx> |
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Subject: |
[Xen-devel] Re: [PATCH V2] pv-grub: Fix for incorrect dom->p2m_host[] list initialization |
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From: |
Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> |
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Date: |
Tue, 26 Apr 2011 22:58:09 +0200 |
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linux-kernel@xxxxxxxxxxxxxxx, stefano.stabellini@xxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, konrad.wilk@xxxxxxxxxx |
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Tue, 26 Apr 2011 13:59:48 -0700 |
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Mutt/1.5.12-2006-07-14 |
Daniel Kiper, le Tue 26 Apr 2011 20:56:49 +0200, a écrit :
> New time optimized version.
>
> After a lot of debugging and long reading of Linux Kernel and Xen code
> finally I killed deeply hidden bug in pv-grub. Details below.
> Additionally, I am CC'ing this e-mail to LKML because this issue
> looks like Linux Kernel problem, however, it is not.
>
> This patch applies to Xen Ver. 4.0, Xen Ver. 4.1 and Xen unstable tree.
>
> # HG changeset patch
> # User dkiper@xxxxxxxxxxxx
> # Date 1303843062 -7200
> # Node ID c4c2919afe9727e107ad3b862619b40d4731d3e4
> # Parent dbf2ddf652dc3dd927447e79ef4bc586de55d708
> Introduction of Linux Kernel git commit
> ceefccc93932b920a8ec6f35f596db05202a12fe
> (x86: default CONFIG_PHYSICAL_START and CONFIG_PHYSICAL_ALIGN to 16 MB)
> revealed
> deeply hidden bug in pv-grub. During kernel load stage dom->p2m_host[] list
> has
> been incorrectly initialized.
>
> At the beginning of kernel load stage dom->p2m_host[] list is populated with
> current PFN->MFN layout. Later during memory allocation (memory is allocated
> page by page in kexec_allocate()) page order is changed to establish linear
> layout in new domain. It is done by exchanging subsequent MFNs with newly
> allocated MFNs. dom->p2m_host[] list is indexed by currently requested PFN
> (it is incremented from 0) and PFN of newly allocated paged. If PFN of newly
> allocated page is less than currently requested PFN then earlier allocated
> MFN is overwritten which leads to domain crash later. This patch corrects
> that issue. If PFN of newly allocated page is less then currently requested
> PFN then relevant PFN/MFN pair is properly calculated and usual exchange
> occurs later.
>
> Signed-off-by: Daniel Kiper <dkiper@xxxxxxxxxxxx>
Reviewed-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
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