On 08/14/2012 05:38 PM, Michael S. Tsirkin wrote:

And even ignoring that, global pointer to a device
is an ugly hack and ugly hacks tend to explode.

And even ignoring estetics, and if we decide we are fine
with a single balloon, it needs to fail gracefully not
crash like it does now.

Fair enough.  That certainly seems easy enough to fix.

Each balloon driver can have its own struct address_space,
and simply point mapping->host (or any of the others) at
a global balloon thing somewhere.

if (page->mapping && page->mapping->host == balloon_magic)