Re: port-xen/49869: Xen DomU fails to crash dump

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

The following reply was made to PR port-xen/49869; it has been noted by GNATS.

From: Manuel Bouyer <bouyer%antioche.eu.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: port-xen-maintainer%NetBSD.org@localhost, gnats-admin%NetBSD.org@localhost,
        netbsd-bugs%NetBSD.org@localhost
Subject: Re: port-xen/49869: Xen DomU fails to crash dump
Date: Sun, 3 May 2015 23:19:56 +0200

 On Sat, May 02, 2015 at 07:50:00AM +0000, mlelstv%serpens.de@localhost wrote:
 > >Description:
 > Neither a i386 nor a amd64 DomU are able to dump core after a system
 > panic.
 > 
 > amd64 provides an empty memory map (dumpsize = 0) to the dump functions.
 > These will then just abort with the message "not possible".
 > 
 > i386 panics when you try to run the 'sync' command in ddb.
 
 this is a known issue. From memory, the problem is with the pa -> ma
 translation. This may be fixable without too much work, but then there
 woukd be another problem:
 the MI dump functions (and also /dev/mem) uses PA addresses
 as offsets, but some pointers (including the page tables) uses MA
 addresses. This basically means that the dump would be unusable.
 This is not easy to fix and would require changes to the crash
 dump analysis tools.
 
 -- 
 Manuel Bouyer <bouyer%antioche.eu.org@localhost>
      NetBSD: 26 ans d'experience feront toujours la difference
 --