RE: [Xen-devel] "Iomem mapping not permitted" during windows crash dump under GPLPV

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> James Harper wrote:
> >> Keir Fraser wrote:
> >>> On 30/01/2010 08:30, "James Harper"
<james.harper@xxxxxxxxxxxxxxxx>
> > wrote:
> >>>> So there is definitely nothing I could tell Xen to do with a DomU
> > PFN
> >>>> that would remove the p2m mapping?
> >>> If you balloon out a page, that would do it.
> >>>
> >> Yes, it certainly would and I've seen it many times. I'm fairly
sure
> >> that by just ignoring the failed block writes coming back from
> >> blkback/tap and carrying on you still end up with a usable
MEMORY.DMP
> >> after reboot.
> >>
> >
> > Yes, that works. I still eye the error messages with contempt though
:)
> >
> 
> If you wanted to be clean, I guess you could check the data buffer
addr
> passed to you by Windows against a map of ballooned out pages and
> substitute a dummy buffer in this case... but then you have the
> 'interesting' problem of making the dump driver aware of that map.
> 

Someone on the ntdev list suggested that one approach could be to
allocate a single page at setup time and map that into each 'hole' I
leave behind by ballooning pages out. I haven't checked if Xen supports
a HVM DomU randomly mapping pages like that and if it will let it map
the same page multiple times, but it would remove the errors and keep
everything happy.

James


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel