Re: [Xen-devel] Re: [RFC PATCH 18/35] Support gdt/idt/ldt handling on Xen.

Andi Kleen
2006-03-22T18:09:02Z

On Wednesday 22 March 2006 18:51, Zachary Amsden wrote:

>
> Yes, trapping works fine. Even LLDT is infrequent.

Not when you use old style LinuxThreads which use the LDT for TLS.

> No. First, you have to create a special #GP handler for the general
> protection fault.

[... etc ...]

Sure but Xen already has the infrastructure for all of this and last
time I checked it was approaching and exceeding the size of the main
core kernel so a bit more of instruction emulation probably wouldn't
do too much harm.

In general I think any x86 hypervisor that attempts to work
on current platforms needs instruction emulation because it is
the only way to virtualize IO devices.

If this was supposed to be a interface for lots of hypervisors then maybe,
but so far it seems to only cover Xen and possibly some other bloatware
ones.

That said I don't feel very strongly about emulating these instructions
or not as long as they can do that without too much code duplication.
The current patch are still a bit too excessive on the duplication front.

-Andi