Date: Thu, 24 Mar 2011 00:46:25 +0200 From: Andriy Gapon <avg@freebsd.org> To: Peter Wemm <peter@wemm.org> Cc: Alexander Best <arundel@freebsd.org>, bz@freebsd.org, Oliver Fromme <olli@lurza.secnetix.de>, freebsd-arch@freebsd.org Subject: Re: kernel memory checks on boot vs. boot time Message-ID: <4D8A7841.5080004@freebsd.org> In-Reply-To: <AANLkTineBMTh3YWEO7TRGzfXHZvj80G9fw01s6z0gkRS@mail.gmail.com> References: <alpine.BSF.2.00.1103221634241.6104@ai.fobar.qr> <201103231029.p2NATtwg090498@lurza.secnetix.de> <20110323171443.GA59972@freebsd.org> <201103231426.27750.jhb@freebsd.org> <AANLkTineBMTh3YWEO7TRGzfXHZvj80G9fw01s6z0gkRS@mail.gmail.com>
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on 23/03/2011 21:28 Peter Wemm said the following: > Part of the reason for this "check" is a sanity check to make sure we > enumerated memory correctly and that we have at least got basic ram > functionality. The existence of hw.physmem complicates this. On > machines where hw.physmem could be used to tell the kernel that there > was more ram present than the kernel enumerates (old bioses etc), this > was kind of important to sanity check. > > Even though modern hardware will fail windows compliance tests if the > SMAP etc is wrong, never underestimate the ability of bios makers to > find new and bizarre ways of screwing things up. > > I'd kinda like to keep a basic "is this real, non mirrored ram?" test > there. eg: the 2-pass step of writing physical address into each page > and then checking that they are still there on the second pass. > > Oh, did I mention the machine where the ACPI bios info tells the OS > that the current state is S3 (suspended to ram) instead of S0? > > When the kernel blows up at boot without a message.. we get the blame, > not the bios maker. I hear what you are saying, but is there any other OS that takes this level of responsibility? Should we either? I mean, hardware and BIOS vendors can screw up things in very creative ways and it's impossible to protect against that. When we are bug-compatible with some other OS, then it's one thing; but when we try to to be even "better" than that, that's quite another thing. -- Andriy Gapon
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