Date: Wed, 2 Dec 1998 20:46:45 +1100 From: Peter Jeremy <peter.jeremy@auss2.alcatel.com.au> To: mike@smith.net.au Cc: current@FreeBSD.ORG Subject: Re: sio breakage Message-ID: <98Dec2.204608est.40351@border.alcanet.com.au>
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Mike Smith <mike@smith.net.au> wrote: > I suspect that the problem is that the i386 >doesn't trap attempts to clear PSL_I if PSL_IOPL is set, so you can't >guarantee that this will be detected cleanly. If you aren't running at IOPL, CLI and STI will trap, but POPF _ignores_ any attempt to change PSL_I. This particular brokenness in POPF (and the inability to make PUSHF trap) is all that prevents us easily providing a virtual-386 environment (which means you could just run buggy, half-baked file-loaders, rather than trying to emulate all their undocumented interfaces). [Actually, I gather that Pentium and later chips _do_ have the microcode to allow virtual-386, but the relevant incantations to use this is only available under NDA]. >> I don't believe this is reasonable. We should provide some safe way >> for an application program to execute code with interrupts disabled. >> Amongst other applications, XFree86 needs this. > >It shouldn't (ideally). I agree. And whilst I haven't checked why, XFree86 does appear to disable interrupts at times. > If it does, this is clearly indicative of a >need to move some of the server code into the kernel, You mean, like GGI <http://www.ggi-project.org/>; :-). Peter -- Peter Jeremy (VK2PJ) peter.jeremy@alcatel.com.au Alcatel Australia Limited 41 Mandible St Phone: +61 2 9690 5019 ALEXANDRIA NSW 2015 Fax: +61 2 9690 5247 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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