Xen devel - Oct 2010 - c/s 21886 change to DMAR table hiding

Keir,

In c/s 21886, you changed the method by which the DMAR ACPI table was hidden
from dom0.  Why was this change needed?
-    dmar->header.signature[0] = ''\0'';
+    dmar->header.signature[0] = ''X'';
+    dmar->header.checksum -= ''X''-''D'';

I ask because tboot was using the original method to unhide/re-hide the table
during S3 (because the TXT launch on S3 resume requires a valid DMAR table) and
this has broken S3 w/ TXT.

Joe

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On 10/29/10 08:06, Cihula, Joseph wrote:
> Keir,
>
> In c/s 21886, you changed the method by which the DMAR ACPI table was
hidden from dom0.  Why was this change needed?
> -    dmar->header.signature[0] = ''\0'';
> +    dmar->header.signature[0] = ''X'';
> +    dmar->header.checksum -=
''X''-''D'';
>
> I ask because tboot was using the original method to unhide/re-hide the
table during S3 (because the TXT launch on S3 resume requires a valid DMAR
table) and this has broken S3 w/ TXT.
Please see discussion under
http://lists.xensource.com/archives/html/xen-devel/2010-07/msg01517.html

Problem was crash kernel not comig up with the original DMAR hide.


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
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Fujitsu Technology Solutions              e-mail: juergen.gross@ts.fujitsu.com
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