Re: [Xen-devel] [PATCHv2] x86: map portion of kexec crash area that is within the direct map area

[Daniel Kiper <daniel.kiper@xxxxxxxxxx>]

On Wed, Jan 08, 2014 at 06:35:19PM +0000, David Vrabel wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>
> Commit 7113a45451a9f656deeff070e47672043ed83664 (kexec/x86: do not map
> crash kernel area) causes fatal page faults when loading a crash
> image.  The attempt to zero the first control page allocated from the
> crash region will fault as the VA return by map_domain_page() has no
> mapping.
>
> The fault will occur on non-debug builds of Xen when the crash area is
> below 5 TiB (which will be most systems).
>
> The assumption that the crash area mapping was not used is incorrect.
> map_domain_page() is used when loading an image and building the
> image's page tables to temporarily map the crash area, thus the
> mapping is required if the crash area is in the direct map area.
>
> Reintroduce the mapping, but only the portions of the crash area that
> are within the direct map area.
>
> Reported-by: Don Slutz <dslutz@xxxxxxxxxxx>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> Cc: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> ---
> This fixes a Xen crash so is an important fix for the 4.4 release..

Thanks. It looks quite good for me but I would like to do some tests.
I will send you results by the end of this week.

Daniel

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