From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: vga passthrough // questions about pci passthrough Date: Fri, 28 Sep 2012 18:29:26 +0200 Message-ID: <5065D066.4030006@siemens.com> References: <50064D87.2090809@adiumentum.com> <50068134.4060306@siemens.com> <5006A72D.3080408@adiumentum.com> <5006ADF3.9030304@adiumentum.com> <1342621405.2229.194.camel@bling.home> <50081FBC.7060208@adiumentum.com> <1342714590.3142.4.camel@ul30vt> <5064364E.7050508@adiumentum.com> <1348768586.2320.204.camel@ul30vt.home> <50649E5C.6020808@adiumentum.com> <1348773491.2320.217.camel@ul30vt.home> <50655BE6.9050305@siemens.com> <1348847417.2320.333.camel@ul30vt.home> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Martin Wolf , "kvm@vger.kernel.org" To: Alex Williamson Return-path: Received: from goliath.siemens.de ([192.35.17.28]:16646 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758533Ab2I1Q3c (ORCPT ); Fri, 28 Sep 2012 12:29:32 -0400 In-Reply-To: <1348847417.2320.333.camel@ul30vt.home> Sender: kvm-owner@vger.kernel.org List-ID: On 2012-09-28 17:50, Alex Williamson wrote: > On Fri, 2012-09-28 at 10:12 +0200, Jan Kiszka wrote: >> On 2012-09-27 21:18, Alex Williamson wrote: >>> On Thu, 2012-09-27 at 20:43 +0200, Martin Wolf wrote: >>>> thank you for the information. >>>> >>>> i will try what you mentioned... >>>> do you have some additional information about rebooting a VM with a >>>> passed through videocard? >>>> (amd / ati 7870) >>> >>> I don't. Is the bsod on reboot only or does it also happen on shutdown? >>> There's a slim chance it could be traced by enabling debug in the >>> pci-assign driver and analyzing what the guest driver is trying to do. >>> I'm hoping that q35 chipset support might resolve some issues with vga >>> assignment as it exposes a topology that looks a bit more like one that >>> a driver would expect on physical hardware. Thanks, >> >> From our attempts to get more working than what NVIDIA Quadro cards >> support officially, my own experiments with q35 in this context and our >> discussions with NVIDIA, I'm pretty skeptical that this chipset will >> make a difference here. Most problems are due to those non-standard side >> channels to configure the hardware, memory mappings etc. And getting >> this working requires either cooperation of the vendor or *a lot* of >> reverse engineering. > > I heard from an nvidia guy that the driver behaves differently depending > on whether it finds an upstream express port, so we're probably causing > ourselves more problems if it's trying to run in AGP mode. May be a point for the low- to mid-range cards. It does not apply to the "virtualization-ready" Quadro series according to our information back then. > There was > also a lot of FUD in Xen (maybe justified) around how the BIOS > determines the memory ranges and whether it bypasses the PCI BARs and > gets them directly. That means some cards may require identity mapping > to work. It seems like the very high-end cards are possibly fixing > this, but they're far more expensive than I can justify. Thanks, Yes, that is what makes them virtualization ready. But they also come with limitations. So far, you can't pass-through a primary card or use it for early boot messages of the guest as the BIOS is not ready for that - without identity mapping or even more. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux