From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [PATCH 2/2] iommu: dmar -- reserve mmio space used by IOMMU Date: Wed, 6 Jun 2012 10:16:00 +0200 Message-ID: <20120606081600.GB5991@gmail.com> References: <1338845342-12464-1-git-send-email-ddutile@redhat.com> <1338845342-12464-3-git-send-email-ddutile@redhat.com> <1338849430.10884.288.camel@shinybook.infradead.org> <4FCD401D.9000304@redhat.com> <1338852196.26785.10.camel@shinybook.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: Content-Disposition: inline In-Reply-To: <1338852196.26785.10.camel-Fexsq3y4057IgHVZqg5X0TlWvGAXklZc@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: David Woodhouse Cc: chrisw-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, suresh.b.siddha-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, mingo-X9Un+BFzKDI@public.gmane.org List-Id: iommu@lists.linux-foundation.org CiogRGF2aWQgV29vZGhvdXNlIDxkd213MkBpbmZyYWRlYWQub3JnPiB3cm90ZToKCj4gPiB3ZWxs LCBvbmUgY291bGQgYXJndWUgaXQgbWF5IGJlIGVhc2llciB0byBjbGFpbSB0aGUgc3BhY2UgCj4g PiByZXNlcnZlZCBpbiB0aGUgT1MgdGhlbiBtYWtpbmcgeWV0IGFub3RoZXIgaG9sZSBpbiB0aGUg Cj4gPiBhdmFpbGFibGUgSU8gYWRkcmVzcyBzcGFjZSBpbiB0aGUgQUNQSSB0YWJsZXMuCj4gCj4g QnV0IGhvdz8gSXQncyBnb3QgdG8gd29yayB3aXRoIG9wZXJhdGluZyBzeXN0ZW1zIHRoYXQgcHJl ZGF0ZSAKPiB0aGUgSU9NTVUuIFRoZSByZWdpc3RlcnMgKmhhdmUqIHRvIGJlIGluIGEgbWFya2Vk IGhvbGUuIElmIAo+ICpub3QqLCB0aGVuIHdlIHNob3VsZCBnaXZlIGEgY2xlYXIgIllPVVIgQklP UyBJUyBCUk9LRU4iIAo+IG91dHB1dCBsaWtlIGFsbCB0aGUgc2ltaWxhciBicmVha2FnZXMsIGFu ZCBkbyBvdXIgYmVzdCB0byB3b3JrIAo+IGFyb3VuZCBpdC4KPiAKPiBXb3JraW5nIGFyb3VuZCBp dCBpcyBmaW5lOyBJJ20gbm90IHN1Z2dlc3RpbmcgdGhhdCB3ZSBzaG91bGQgCj4gV0FSTigpICpp bnN0ZWFkKiBvZiB3b3JraW5nIGFyb3VuZCBpdC4KClNvIGJhc2ljYWxseSB0aGUgcGF0Y2gtc2V0 IGlzIGZpbmUgYXMtaXMsIHdlIGp1c3Qgd2FudCBhIApzdWZmaWNpZW50bHkgbmFzdHkgc291bmRp bmcgd2FybmluZyBtZXNzYWdlIGFib3V0IHRoZSBCSU9TIGJ1ZywgCndpdGggYWN0aW9uYWJsZSBv dXRwdXQsIHNvbWV0aGluZyBsaWtlOgoKICAgICAuLi4gdGhlIGtlcm5lbCBpcyBzYWQgYmVjYXVz ZSBhIGJ1Z2d5IEJJT1MgaGFzIG5vdCAKICAgICAgICAgbWFya2VkIElPTU1VIGFyZWEgeHh4LXl5 eSBhcyByZXNlcnZlZCwgd29ya2luZwogICAgICAgICBpdCBhcm91bmQuIFlvdSBnZXQgdG8ga2Vl cCBhbGwgdGhlIHBpZWNlcyBhbmQKICAgICAgICAgYmUgbW9yZSBjYXJlZnVsIHdpdGggcmVtYWlu aW5nIGV5ZS4KCihvciBhIGZ1bmN0aW9uYWwgZXF1aXZhbGVudCB0aGVyZW9mLikKCnRoaXMgcGF0 Y2ggY291bGQgYmUgYWRkZWQgYXMgYSB0aGlyZCBwYXRjaCBpbiB0aGUgc2VyaWVzLCByaWdodD8K Cj4gPiAgIFRoZSBCSU9TJ3MgYXJlIGdldHRpbmcgYmV0dGVyLCBidXQgSSd2ZSBzZWVuIHR1cnRs ZXMgcnVuIAo+ID4gICBmYXN0ZXIuLi4gOy0pIC4KPiAKPiBUaGFua2Z1bGx5LCB0aGVyZSBhcmUg bm93IHNvbWUgbW9kZXJuIEludGVsIHN5c3RlbXMgb24gd2hpY2ggCj4geW91IGNhbiBydW4gQ29y ZWJvb3QuIFRoaXMgc2hvdWxkIGJlIGEgaHVnZSBiZW5lZml0IOKAlCB5b3UgCj4gc2hvdWxkIGJl IGFibGUgdG8gYnVpbGQgYW4gdXAtdG8tZGF0ZSBUaWFub2NvcmUgYW5kIGRlcGxveSBpdCAKPiBh cyB5b3VyIENvcmVib290IHBheWxvYWQsIHJhdGhlciB0aGFuIGhhdmluZyB0byBwdXQgdXAgd2l0 aCAKPiB0aGUgY3JhcCB0aGF0J3Mgb24gdGhlIHN5c3RlbSB3aGVuIHlvdSByZWNlaXZlIGl0LgoK SWYgd2UgY291bGQgaW50ZWdyYXRlIENvcmVib290IGludG8gdGhlIGtlcm5lbCBhbmQgY291bGQg YnVpbGQgYSAKYnpJbWFnZSB0aGF0IG9uZSBjb3VsZCB3cml0ZSBpbnRvIHRoZSBCSU9TIGZsYXNo IGltYWdlIGFuZCB0aHVzIApoYXZlIGFuIHVwZGF0ZWQgYW5kIGZ1bmN0aW9uYWwgQklPUywgdGhh dCB3b3VsZCBiZSBhd2Vzb21lLgoKUGVvcGxlIGNvdWxkIGFjdHVhbGx5IHdyaXRlIHN5c3RlbXMg d2l0aCBwcm9wZXIgJ2V2ZXJ5IHBpeGVsIGlzIApwZXJmZWN0JyBib290IG91dHB1dCBhbmQgbG93 IGxhdGVuY3kgYmVoYXZpb3IgZnJvbSB0aGUgbW9tZW50IApwb3dlciBpcyB0dXJuZWQgb24gdG8g dGhlIGZpcnN0IGRlc2t0b3AgR1VJIGZyYW1lIGFuZCBzdWNoLgoKKFdpdGggc29tZSBmYWlsIHNh ZmUgbWVjaGFuaXNtIGZvciBidWdzLikKCkFuZCBwb25pZXMuCgpUaGFua3MsCgoJSW5nbwpfX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fXwppb21tdSBtYWlsaW5n IGxpc3QKaW9tbXVAbGlzdHMubGludXgtZm91bmRhdGlvbi5vcmcKaHR0cHM6Ly9saXN0cy5saW51 eGZvdW5kYXRpb24ub3JnL21haWxtYW4vbGlzdGluZm8vaW9tbXU= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754881Ab2FFIQN (ORCPT ); Wed, 6 Jun 2012 04:16:13 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:45025 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754698Ab2FFIQF (ORCPT ); Wed, 6 Jun 2012 04:16:05 -0400 Date: Wed, 6 Jun 2012 10:16:00 +0200 From: Ingo Molnar To: David Woodhouse Cc: Don Dutile , iommu@lists.linux-foundation.org, mingo@elte.hu, linux-kernel@vger.kernel.org, chrisw@redhat.com, suresh.b.siddha@intel.com Subject: Re: [PATCH 2/2] iommu: dmar -- reserve mmio space used by IOMMU Message-ID: <20120606081600.GB5991@gmail.com> References: <1338845342-12464-1-git-send-email-ddutile@redhat.com> <1338845342-12464-3-git-send-email-ddutile@redhat.com> <1338849430.10884.288.camel@shinybook.infradead.org> <4FCD401D.9000304@redhat.com> <1338852196.26785.10.camel@shinybook.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1338852196.26785.10.camel@shinybook.infradead.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * David Woodhouse wrote: > > well, one could argue it may be easier to claim the space > > reserved in the OS then making yet another hole in the > > available IO address space in the ACPI tables. > > But how? It's got to work with operating systems that predate > the IOMMU. The registers *have* to be in a marked hole. If > *not*, then we should give a clear "YOUR BIOS IS BROKEN" > output like all the similar breakages, and do our best to work > around it. > > Working around it is fine; I'm not suggesting that we should > WARN() *instead* of working around it. So basically the patch-set is fine as-is, we just want a sufficiently nasty sounding warning message about the BIOS bug, with actionable output, something like: ... the kernel is sad because a buggy BIOS has not marked IOMMU area xxx-yyy as reserved, working it around. You get to keep all the pieces and be more careful with remaining eye. (or a functional equivalent thereof.) this patch could be added as a third patch in the series, right? > > The BIOS's are getting better, but I've seen turtles run > > faster... ;-) . > > Thankfully, there are now some modern Intel systems on which > you can run Coreboot. This should be a huge benefit — you > should be able to build an up-to-date Tianocore and deploy it > as your Coreboot payload, rather than having to put up with > the crap that's on the system when you receive it. If we could integrate Coreboot into the kernel and could build a bzImage that one could write into the BIOS flash image and thus have an updated and functional BIOS, that would be awesome. People could actually write systems with proper 'every pixel is perfect' boot output and low latency behavior from the moment power is turned on to the first desktop GUI frame and such. (With some fail safe mechanism for bugs.) And ponies. Thanks, Ingo