While doing so I realized that this would fit well with the suggested HVM
related changes in my other response. However, you seem to indicate that such changes aren't worth it from a performance perspective, so I'm not sure it'd be worth. Otoh, in a long lived production environment fragmentation is likely to become a significant issue, and it is certainly not desirable to have good chances of HVM domain creation starting to fail after a system has been up for a long time (in theory it might be necessary to balloon out of Dom0 three quarters of the installed physical memory plus one quarter of the to be allocated amount in order to guarantee that shadow allocation can succeed). But I also agree that any attempt to change this without changing the parts of the shadow code that depend on non-zero order pages will only reduce the likelihood of running into the problem, it won't eliminate it. So I guess for a first cut I'll go with your suggestion of removing the 'order' parameter of shadow_prealloc().

Jan