From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Airlie Subject: Re: [Bug #12608] 2.6.29-rc powerpc G5 Xorg legacy_mem regression Date: Fri, 6 Feb 2009 07:45:05 +1000 Message-ID: <21d7e9970902051345h76fb26c1hc0397f6262f70eae@mail.gmail.com> References: <1233791329.4612.23.camel@pasglop> <1233867944.4612.104.camel@pasglop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=qHTNwvZlGyHWYDi98yAZHLfahBWp2qBlPJGgt9+ghPI=; b=k+ZJkqtv3sM4i6vEZRuMDTrdlVv6jLxd5eDnREcgE8z92dQ7DuV3wTqhBKwSSKcmeH TrRWnKx5Jhv1yiGPaQG5P7RgNn8OBQ4K7CdGF3Nha0PUGPhK2Lu7+OsIHpDb5AwAK+wv XfiSiPwWZVmuRw4KVoEQunQGZtOlTJ8OkM/OM= In-Reply-To: <1233867944.4612.104.camel@pasglop> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Benjamin Herrenschmidt Cc: Hugh Dickins , "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Jesse Barnes On Fri, Feb 6, 2009 at 7:05 AM, Benjamin Herrenschmidt wrote: > >> Is it a really a bug in X, or a misunderstanding between X and >> the kernel as to what existence of the legacy_mem file implies? >> >> I may have got this quite wrong, but to me it appears that X assumes >> that existence of the legacy_mem file implies that it will be useful; >> whereas the kernel thinks it can make the legacy_mem file available, >> even if it cannot be used for mmapping mem - which is its sole purpose? >> >> What if pci_create_legacy_files() were to call some new verification >> routine, and only create the legacy_mem file if it would be usable? >> (But perhaps that cannot be known at the time it needs to be created.) > > Well, first X should certainly not -fail- to launch if it fails to map > legacy memory, which is generally not useful anyway. That's where the > bug is. Jesse, did you have a chance to fix that yet or should I give it > a go ? > > The second problem is that if I just don't expose the legacy_mem file, > then X has no way to know whether the kernel doesn't support the > interface or whether the HW doesn't support legacy memory access. So X > will fallback to whacking /dev/mem which is even more bogus. At least > that's what I remember from last I looked at that part of X code. > > It should be a trivial fix on X side tho. I think the correct answer is the ugly one, try again. Add a new legacy_mem interface that works cleanly, update X to use it, leave the old broken one broken as it for older X to use. Dave. > > Cheers, > Ben. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >