Date: Wed, 22 Sep 2004 10:57:08 -0700 From: Nate Lawson <nate@root.org> To: Bruce M Simpson <bms@spc.org> Cc: Roman Kurakin <rik@cronyx.ru> Subject: Re: mp_machdep.c (was Re: [Fwd: Re: Bug reports requested - acpi]) Message-ID: <4151BCF4.6070501@root.org> In-Reply-To: <20040922090406.GF4985@empiric.icir.org> References: <41421D6A.8070805@cronyx.ru> <41505663.40407@cronyx.ru> <4150607D.3020900@root.org> <200409211441.42325.jhb@FreeBSD.org> <20040922090406.GF4985@empiric.icir.org>
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Bruce M Simpson wrote: > On Tue, Sep 21, 2004 at 02:41:42PM -0400, John Baldwin wrote: >>Umm, 0xa0000 is the start of Video RAM, so I sure hope the ACPI wake code >>doesn't try to write code into Video memory. The pmap_invalidate_page is >>certainly needed. > > This is more common than you'd think, by the way. The 0xA0000 range is > sometimes used as a place to hold 'hidden memory' used whilst servicing > an SMI; ie the pages are 'stolen' from main memory by the during BIOS > initialization using registers for APM/ACPI support in the chipset. > > Sometimes this is referred to as SMRAM or Systems Management Memory (SMM). > I posted some code just over a year ago illustrating how to access this > 'hidden segment' on the i440BX to the lists. Thanks, I work with SMIs a lot. :) The DDJ article is a good intro: http://www.rcollins.org/ddj/Jan97/Jan97.html -- Nate
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