From: Ingo Molnar <mingo@elte.hu>
To: Kirill Korotaev <dev@sw.ru>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [announce, patch] 4G/4G split on x86, 64 GB RAM (and more) support
Date: Thu, 10 Jul 2003 12:59:24 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.44.0307101248480.5443-100000@localhost.localdomain> (raw)
In-Reply-To: <200307101450.42340.dev@sw.ru>
On Thu, 10 Jul 2003, Kirill Korotaev wrote:
> > yes, it is also visible to user-space, otherwise user-space LDT
> > descriptors would not work. The top 16 MB of virtual memory also hosts the
> > 'virtual LDT'.
> > the top 16 MB is split up into per-CPU areas, each CPU has its own. Check
> > out atomic_kmap.h for details.
> But you need to remap it every time a switch occurs. [...]
only if the task uses an LDT - which with NPTL is very rare these days.
But _if_ something relies on LDTs heavily then it can be done limit-less.
(we used to have nasty LDT limits due to vmalloc() limitations).
> 8. NMI is special. The only difference is that unlike usual interrupts
> NMI can interrupt returning to user-space either. This is solved easily
> by saving current cr3/esp on enter and restoring them if required on
> leave ("required" == esp >= 0xffxxxxxx).
ok, "esp >= 0xff000000" is a good check, and it's a constant check so it
can be done very early in the entry code. The double-cr3-load is not an
issue, this is a rare race situation. I'll rework this area to be faster,
but first i wanted to concentrate on robustness. Thanks for you comments,
they are really useful!
Ingo
next prev parent reply other threads:[~2003-07-10 10:47 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-09 10:58 [announce, patch] 4G/4G split on x86, 64 GB RAM (and more) support "Kirill Korotaev"
2003-07-09 15:14 ` Ingo Molnar
2003-07-10 10:50 ` Kirill Korotaev
2003-07-10 10:59 ` Ingo Molnar [this message]
2003-07-10 11:35 ` Russell King
2003-07-10 12:33 ` Kirill Korotaev
2003-07-14 20:24 ` Ingo Molnar
[not found] <E19aCeB-000ICs-00.kksx-mail-ru@f23.mail.ru.suse.lists.linux.kernel>
2003-07-09 12:44 ` Andi Kleen
[not found] ` <200307091851.33438.dev@sw.ru>
[not found] ` <20030709164852.523093a3.ak@suse.de>
2003-07-09 15:17 ` Kirill Korotaev
-- strict thread matches above, loose matches on Subject: below --
2003-07-08 22:45 Ingo Molnar
2003-07-09 1:29 ` William Lee Irwin III
2003-07-09 5:13 ` Martin J. Bligh
2003-07-09 5:19 ` William Lee Irwin III
2003-07-09 5:43 ` William Lee Irwin III
2003-07-12 23:58 ` Davide Libenzi
2003-07-13 0:11 ` William Lee Irwin III
2003-07-13 8:13 ` jw schultz
2003-07-09 6:42 ` Ingo Molnar
2003-07-09 5:16 ` Dave Hansen
2003-07-09 7:08 ` Geert Uytterhoeven
2003-07-10 1:36 ` Martin J. Bligh
2003-07-10 13:36 ` Martin J. Bligh
2003-07-13 22:05 ` Petr Vandrovec
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