Date: Tue, 28 Oct 2003 01:27:19 -0800 From: Marcel Moolenaar <marcel@xcllnt.net> To: Doug Rabson <dfr@nlsystems.com> Cc: cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/ia64/ia64 sys_machdep.c src/sys/ia64/include sysarch.h Message-ID: <20031028092719.GA44213@dhcp01.pn.xcllnt.net> In-Reply-To: <1067332169.42914.3.camel@herring.nlsystems.com> References: <200310272254.h9RMsZFN027412@repoman.freebsd.org> <1067332169.42914.3.camel@herring.nlsystems.com>
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On Tue, Oct 28, 2003 at 09:09:29AM +0000, Doug Rabson wrote: > Shouldn't there some kind of access control here? It appears as if > anyone at all can do inx/outx. Eventually, yes. There's a possibility that I remove these. The X server needs to be able to mmap uncachable memory for access to the hardware. This could also be used to do I/O. The only thing the kernel needs to export is the base of the memory mapped I/O space with sysctl in that case. Note that this affects the VM and PMAP interfaces :-( > Also, I have a vague feeling that the > Linux kernel manages to support userland inx/outx without system calls - > if so, how do they do that? I think mmap is used for that as well. > Possibly with modern hardware the cost of the bus transaction dwarfs the > cost of doing a system call so perhaps it doesn't matter. The sysarch approach is not optimal. I don't think it's very performance critical. Modern graphics hardware is memory mapped anyway. -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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