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    SubjectRE: local APIC may cause XFree86 hang

    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.


    > -----Original Message-----
    > From: Linus Torvalds []
    > Sent: Wednesday, November 13, 2002 4:48 PM
    > To: Nakajima, Jun
    > Cc:
    > 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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