I noticed one curious thing while working on some issues with Fedora.
At least in 2.6.17-1.2302_FC6xen, the following evaluates to false:
 if (xen_feature(XENFEAT_auto_translated_physmap))
 return pfn;
But the head-xen.S looks like this:
.section __xen_guest
 .ascii "GUEST_OS=linux,GUEST_VER=2.6"
 .ascii ",XEN_VER=xen-3.0"
 .ascii ",VIRT_BASE=0x"; utoh __START_KERNEL_map
 .ascii ",HYPERCALL_PAGE=0x"; utoh (phys_hypercall_page >> PAGE_SHIFT)
 .ascii ",FEATURES=writable_page_tables"
 .ascii "|writable_descriptor_tables"
 .ascii "|auto_translated_physmap"
 .ascii "|supervisor_mode_kernel"
 .ascii ",LOADER=generic"
 .byte 0
Everything continues to work just fine, thanks to runtime checks
of xen_feature() like the above.
So I am curious, if this is something anyone cares about.
Also, why does it happen? If it's a feature which cannot be enabled
(anymore), perhaps we can simply the code and get some performance
by removing the run-time checks.
Greetings,
-- Pete
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