Re: 2.6.18-rc6-mm1: GPF loop on early boot

Ingo Molnar wrote:

yes - but loading a null selector is a special-case: you dont have to invalidate/reload the shadow, you just have to turn access off. This might or might not make a difference on modern CPUs (it makes a difference with older CPUs) - but it's worth a try nevertheless. You measured a 9 cycles degradation with the %gs method, we could recover some of that.

It's a worthwhile experiment. The gain would be the NULL selector load, but the loss would be an additional segment reload on context switch and TLS ABI incompatibility (which is more difficult to quantify).

First step is to make sure the PDA is set up before hitting C code...

   J
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