Messages in this thread | | | Date | Sun, 04 Nov 2007 15:50:14 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] fix i486 boot failure due to stale %ds |
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Jeremy Fitzhardinge wrote: >> Maybe not. I had a look in Intel's SDM Vol3, and the >> section "switching to protected mode" specifies that >> a move to %cr0 that sets PE should immediately be >> followed by a far jmp or call. > > Yes, that's what the spec says. I queried this a few months ago, but > hpa used his convincing voice and said that in practice it isn't > necessary; there are no known cpus which need this, and any that do > would cause other things to break. But I guess now we have the > counter-example...
Joy. Apparently the Intel documentation is actually self-inconsistent. Section 9.9.1, page 9-17 does indeed have the "far jump or call" injunction, whereas the sample code in section 9.10.1, page 9-27, line 180 does a near jump!
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