Re: [Xen-devel] Error restoring DomU when using GPLPV

[ANNIE LI <annie.li@xxxxxxxxxx>]

Hi,
> Actually of course you do the right thing with the shinfo page, so actually
> one page per migration does get switched back to being a Xenheap page (the
> shinfo page) and tot_pages actually increases by 3 on the first migration,
> then decreases by 1 when shinfo gets remapped by the PV drivers. Then
> increases by 1 on every future migration (which is the shinfo Xenheap page
> getting changed into a domheap page), and then decreases by 1 when shinfo
> gets remapped by the PV drivers.
>
> But even setting things out exactly right as above, the end result is the
> same: I *still* cannot explain Annie's result.
The root cause is that winpv driver did not re-map gnttab frames during 
resuming.
Thanks Mukesh very much.

My initial implementation was to map all 32 grant table pages during 
initialization, and then balloon down
those pages during driver first load. However,  i leaked those 32 grant 
pages if i did not re-map those pages
during resuming. This is why Save/restore can work only once.

My second implementation is to map corresponding grant frames device 
needs instead of all 32 grant table.
But it will leak 2 frames every migration because of missing re-mapping 
grant tables.
Then i tried to re-map the grant table during resuming, and balloon down 
shinfo+gntab driver first load.
I did save/restore several times, did not hit any problem. Furthermore, 
i also tried to map 64 grant table pages
during initialization and ballooned down those pages, all work fine.

I will do more test to make sure it and update here.

Thanks
Annie.

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