Re: address space reorganization

[Jacob Gorm Hansen <jacobg@diku.dk>]

Ian Pratt wrote:

> That works OK for the kernel, but you might have user space apps that
> have adapted their behviour based on what the've found in /proc/cpuinfo.

A compromise then would be to lie to userspace and still recalibrate the 
kernel.

> A particularly nasty case is apps or libraries that go at 'cpuid'
> directly, as we can't trap that instruction. I guess VMware have the
> same problem, as I don't believe they translate ring 3 code.

Yeah, nothing we can do there really, except tell people not to :-(

> As regards your proposed critical region, we already effectively do
> this.  We don't recalibrate stuff after a migration yet though (some of
> the tests are quite slow, so I'm not sure you'd want to do them all
> anyhow).

Could perhaps do them in advance, or during the pre-copy phase as they 
are likely to stay constant for the lifetime of the machine, but that 
demands that the receiving side knows what you are looking for.
My system uploads a bootstrapper to the target VM in advance, so I could 
have this info ready when the rest of the OS arrives.

Jacob