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SubjectRE: local APIC may cause XFree86 hang
Date

The one instance I saw was that the BIOS was reading 8254 in a tight loop
for a calibration purpose, and it was assuming the time proceeded in a
constant speed, to exit the loop. In other words, it never assumed it could
get interrupts. To vm86, interrupts are invisible, but they have impacts on
the actual speed.

Jun

> -----Original Message-----
> From: Linus Torvalds [mailto:torvalds@transmeta.com]
> Sent: Wednesday, November 13, 2002 4:48 PM
> To: Nakajima, Jun
> Cc: linux-kernel@vger.kernel.org
> Subject: RE: local APIC may cause XFree86 hang
>
>
> On Wed, 13 Nov 2002, Nakajima, Jun wrote:
> >
> > Are we disabling vm86 code to access to PIT or PIC? I saw some video ROM
> > code (either BIOS call or far call) did access PIT, confusing the OS.
>
> Well, the kernel itself doesn't actually disable/enable anything, it
> leaves that decision to the caller.
>
> XFree86 obviously does have IO rights, and I suspect it may allow the
> video BIOS to do just about anything, simply because it doesn't have much
> choise (the video bios clearly needs a lot of IO privileges too). So yes,
> that could easily confuse the OS if it happens, but it should be
> independent of IO-APIC vs not.
>
> Linus
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