Messages in this thread |  | | Date | Thu, 7 Dec 2000 19:04:12 +0100 (MET) | From | "Maciej W. Rozycki" <> | Subject | Re: Why is double_fault serviced by a trap gate? |
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On Thu, 7 Dec 2000, Petr Vandrovec wrote:
> No. If interrupt uses task gate, task switch happens. Nothing is stored > in context of old process except registers into TSS. There is only one > (bad) problem. If you want to get it 100% proof (it is not needed for double > fault, but it is definitely needed for NMI, as NMI is very often on SMP > ia32), each CPU's IRQ vector must point to different task, otherwise you > can get TSS in use during doublefault, leading to triplefault again...
Well, I expect wasting a descriptor and a page of memory for the purpose of a TSS is not a big problem.
> Yes. Currently if any ESP related problem happens in kernel, machine silently > reboots without any message. With task gate (as Jeff Merkey proposed
You might handle the stack fault with a task gate, actually, but I'm not sure it's worth the hassle. Handling just the double fault should be sufficient.
> some months ago, btw), you can even suspend offending task and recover > from it... I think that also bluesmoke should use task gate, but I > did not read documentation on this yet.
Yep. An MCE is an abort like a double-fault, so the CPU state might be corrupted (by definition -- I have no idea whether it really happens).
-- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +
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