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Date: Mon, 4 Jun 2007 11:49:41 -0400 (EDT) From: Justin Piszcz <jpiszcz@...idpixels.com> To: Ray Lee <ray-lk@...rabbit.org> cc: Jesse Barnes <jbarnes@...tuousgeek.org>, Matt Keenan <tank.en.mate@...il.com>, Andi Kleen <andi@...stfloor.org>, Venki Pallipadi <venkatesh.pallipadi@...el.com>, linux-kernel@...r.kernel.org Subject: Re: Intel's response Linux/MTRR/8GB Memory Support / Why doesn't the kernel realize the BIOS has problems and re-map appropriately? On Mon, 4 Jun 2007, Ray Lee wrote: > On 6/4/07, Jesse Barnes <jbarnes@...tuousgeek.org> wrote: >> On Sunday, June 3, 2007 2:15:06 Matt Keenan wrote: >> > Justin Piszcz wrote: >> > > On Sat, 2 Jun 2007, Andi Kleen wrote: >> > >>> I feel, having a silent/transparent workaround is not a good idea. >> > >>> With that >> > >> >> > >> If enough RAM is chopped off users will notice. They tend to complain >> > >> when they miss RAM. I don't like panic very much because for many >> > >> users it will be a show stopper (even when they are not blessed >> > >> with "quiet" boots like some distributions do) >> > >> >> > >> The message in dmesg could be also emphasized a bit with a little >> > >> ASCII art (but no <blink> tag in there) >> > >> >> > >> The problem I'm more worried about is if the system will be really >> > >> stable --- could it be that the memory controller is still >> > >> misconfigured and cause other stability issues? (we've had such >> > >> cases in the past). Also I'm not sure we can handle the case of >> > >> the MTRR wrong not at the end of memory but at the hole sanely. >> > >> >> > >> -Andi >> > > >> > > So far I have been booting with mem=8832M and have run stress/loaded >> > > the memory subsystem pretty good; what other tests should I run? >> > > >> > > It'd be nice if we could pose some sort of solution/warning for the >> > > future so other people do not have to experience the same problems. >> > > >> > > What are the next steps? >> > >> > Wouldn't it be possible for the e820/MTRR set up code detect the problem >> > and suggest a mem=xxxx that would fix the problem (while also >> > complaining that the BIOS is broken)? >> >> Yes, that should be fairly easy, though as Andi points out, if there are >> holes >> in the MTRR setup, things get a little trickier (I had an earlier patch to >> deal with this, but ended up with too many early boot issues). >> >> Maybe what Venki suggested would be best: just detect the condition and >> panic, with a string telling the user to use mem=xxx (we can figure that >> out) >> and/or upgrade their BIOS. > > Ick. Systems that used to boot fine would then panic on a kernel > upgrade. That's rather rude for a condition that's merely an > optimization (using all memory), rather than one of correctness. A > panic seems entirely inappropriate. > > Ray > While I am unsure of the 'best' solution, if they boot and it does not panic but takes 10 minutes to boot, people are going to seriously wonder what is going on? Justin. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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