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

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

> 
> James Harper wrote:
> >
> > 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.
> >
> 
> Oh that will definitely work but, as I said, the trick is knowing a
> priori where the 'holes' are :-)
> 

The idea would be that I'd map in my dummy page into each hole as I make
them, eg at balloon time. It could in theory be done at dump time but
that's hard, and when a dump occurs you want to do as little as possible
as the system is in an unknown state. All I do at dump time outside of
my vbd driver is event channel notification and grant ref allocation (my
freelist is lock free now so I don't have to worry about spinlocks at
DIRQL anymore). Having to look up a table of pages from another driver
altogether would be painful indeed from a scsiport driver.

James


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