Date: Fri, 28 Dec 2001 23:28:12 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: Peter Wemm <peter@wemm.org> Cc: arch@FreeBSD.ORG, Julian Elischer <julian@elischer.org> Subject: Re: blurk! KSE vs the X86 Message-ID: <XFMail.011228232812.jhb@FreeBSD.org> In-Reply-To: <20011222055111.C28FA38CC@overcee.netplex.com.au>
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On 22-Dec-01 Peter Wemm wrote:
> Julian Elischer wrote:
>>
>> Ok so we have this wonderful thing called a TSS
>> there is one per CPU by default, but you can ask that your process has it
>> own.. that would be one per process.. it has such things as the address
>> to load the system stack pointer from when running your process and take a
>> trap e.g. syscall.
>>
>> This is in the PCB extension area. At this time there is only the
>> capacity to set an extension into the single thread that would want it,
>> and it isn't associated with the process as such via the proc structure,
>> just via the PCB extension pointer. So since threads are transient in KSE
>> processes when the thread migrates away (almost immediatly in some cases)
>> you have no trace of your extension area (hense TSS) so at teh next
>> swtch() it'll be gone again..
>> the QUICK answer is to say that vm86 and KSE can't be mixed, but
>> is that the best solution we can do?
>
> Do not worry about the "best" yet. Lets get a functional baseline
> code set that can actually do an upcall and actually do something useful
> before worrying about this sort of thing.
>
> ie: until we have something functional in the tree, the policy should
> be: KSE is not allowed with {VM86, local LDT, PCB extensions [io port
> access], etc.}
>
> The "best" solution will be apparent after we have got the basics
> working.
LDT is already fine. TSS will be harder as you need a per-process TSS template
that each thread builds its TSS from (possibly on the fly on each kernel
entry/exit).
--
John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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