[Xen-devel] RE: TODO in windows balloon driver

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

> 
> Ye, You are right, it happens when xen doesn't have enough pages for
the VM.
> And windows will crash now.
> 
> In memory overcommit, If there are many VMs on a physical host, and in
dom0
> use a daemon for
> memory managment between VMS, it is possible that xen has no pages for
the VM
> needs memory.
> 
> So I think , it is better to fix it.
> 

I have put your fix in as well as the backoff delay I mentioned earlier,
but I'm reviewing the ballooning stuff now. I can see one bug where I
don't do the initial balloon down in the case of PoD. I've fixed that,
but I'm not doing it early enough, so for Windows 2008 32 bit with
memory=512 and maxmem=1024, Windows still crashes and 'xm dmesg' shows
"Out of populate-on-demand memory!" just after my driver starts to load
(in DriverEntry). It seems to work fine when memory=768 and maxmem=1024
but I still think it could crash on startup if you are unlucky.

The only possible workaround is to do it in DriverEntry of xenpci but
that will require a bit of a refactoring. I think it's probably worth
doing though.

James


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