I've integrated patches from Chris and Martin into the -mm tree. I'll
be sending out the patches shortly after testing with my (still in
progress!) Linux LDT test suite.
First interface quirk came up. It looks like Xen wants to return errors
from hypercalls:
+static inline int install_ldt_entry (__u32 *lp, __u32 entry_1, __u32 entry_2)
+{
+ unsigned long mach_lp = arbitrary_virt_to_machine(lp);
+
+ return HYPERVISOR_update_descriptor(mach_lp, entry_1, entry_2);
+}
While this is fine here, this could be problematic in terms of forcing
error checking in lots of situations where there used to be no error
checking in regular Linux - i.e. GDT updates which fail really are fatal
to the guest, and we don't want to pepper the boot-up code with error
checking where there used to be none.
Also, there is the problem of mapping error codes from the hypervisor
onto error codes for the guest - which could be quite different in
different guests.
One general approach to this is to consider errors as faults to be
delivered to the guest, since in many cases, errors result from
protection violation attempts. This has the benefit of not presenting
the two problems I just mentioned.
For now, the most expedient approach appears to be to preserve the error
code values, but the mapping issue seems to be a large one that needs
long term resolution.
Zach
