From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Graf Subject: Re: PCI passthrough resource remapping Date: Wed, 31 Mar 2010 17:23:11 +0200 Message-ID: <4BB368DF.1060401@suse.de> References: <3b1f68ef1003291600t1175f794vd3f47cdafca48a8@mail.gmail.com> <20100329234752.GM3204@x200.localdomain> <3b1f68ef1003291721v6fcb01edha4f0424ba0ab24f8@mail.gmail.com> <20100330020805.GS3204@x200.localdomain> <3b1f68ef1003301527p2dd9928alf2f6ead85d678634@mail.gmail.com> <20100330235838.GU11934@x200.localdomain> <3b1f68ef1003301747k675f0de0t1b8dec8581e3f4b2@mail.gmail.com> <4BB33F12.1060908@suse.de> <20100331151850.GC25786@x200.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Kenni Lund , kvm list To: Chris Wright Return-path: Received: from cantor2.suse.de ([195.135.220.15]:34692 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755842Ab0CaPXN (ORCPT ); Wed, 31 Mar 2010 11:23:13 -0400 In-Reply-To: <20100331151850.GC25786@x200.localdomain> Sender: kvm-owner@vger.kernel.org List-ID: Chris Wright wrote: > * Alexander Graf (agraf@suse.de) wrote: > >> Kenni Lund wrote: >> >>> 2010/3/31 Kenni Lund : >>> >>> >>>> Booting the guest and tuning to a DVB-T channel _works_ !!! :-D Thanks >>>> a lot for your help...I have one more question, though: If I have two >>>> devices (like the ivtv tuner and the USB card) and they share an IRQ, >>>> if I then assign BOTH of them to the same guest, will it then work? >>>> >>>> Alexander, the patch works, I hope to see it in a stable release in >>>> the near future ;) >>>> >>>> >>> Unfortunately, I have a correction to this :( It _almost_ works. I had >>> some video/audio artifacts which I though was caused by bad reception, >>> but after switching the DVB-T tuner back and forth between the PCI USB >>> card and a laptop, it got clear to me, that this was a passthrough >>> issue. I get no errors in dmesg on the host or in the guest. >>> >>> I recorded a short videoclip which illustrates the issue: >>> https://docs.google.com/leaf?id=0B-_nZameGeN-NDk4YzQ3N2EtMmEzMi00NTU4LWFjMjgtNzkxMzcxYzg2MTM1&hl=en >>> >>> >> Hrm, I'm not sure these would be related to the small BAR region patch. >> It looks more like a timing issue. >> > > small BAR == slow path == timing issue? > Could be, yeah. The only chance I see to avoid that is to have in-kernel small BAR code that would issue the MMIO accesses without the userspace churn. One thing I could imagine would be < PAGE_SIZE memory slots. Then userspace just maps the 4K to the BAR, but passes only a part of it on as slot. Alex