From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: [v8][PATCH 06/16] hvmloader/pci: disable all pci devices conflicting with rdm Date: Thu, 16 Jul 2015 16:39:44 +0100 Message-ID: <55A7D040.809@citrix.com> References: <1437029582-19564-1-git-send-email-tiejun.chen@intel.com> <1437029582-19564-7-git-send-email-tiejun.chen@intel.com> <55A79AFA.3040500@intel.com> <55A7AFF4.1040909@intel.com> <55A7CE890200007800091EC8@mail.emea.novell.com> <55A7B647.8080808@intel.com> <55A7E1C30200007800091F48@mail.emea.novell.com> <55A7CBBA.90606@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55A7CBBA.90606@intel.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "Chen, Tiejun" , Jan Beulich Cc: Wei Liu , Ian Campbell , Stefano Stabellini , George Dunlap , Andrew Cooper , Ian Jackson , "xen-devel@lists.xen.org" , Keir Fraser List-Id: xen-devel@lists.xenproject.org On 07/16/2015 04:20 PM, Chen, Tiejun wrote: >>> What about this? >> >> Looks reasonable (but don't forget that I continue to be unconvinced >> that the patch as a whole makes sense). > > Yes, I always keep this in my mind as I mentioned in patch #00. Any risk > you're still concerning? Is it that case if guest OS force enabling > these devices again? IMO, at this point there are two cases: > > #1. Without passing through a RMRR device > > Those emulated devices don't create 1:1 mapping so its safe, right? > > #2. With passing through a RMRR device > > This just probably cause these associated devices not to work well, but > still don't bring any impact to other Domains, right? I mean this isn't > going to worsen the preexisting situation. > > If I'm wrong please correct me. But I think the issue is, without doing *something* about MMIO collisions, the feature as a whole is sort of pointless. You can carefully specify rdm="strategy=host,reserved=strict", but you might still get devices whose MMIO regions conflict with RMMRs, and there's nothing you can really do about it. And although I personally think it might be possible / reasonable to check in a newly-written, partial MMIO collision avoidance patch, not everyone might agree. Even if I were to rewrite and post a patch myself, they may argue that doing such a complicated re-design after the feature freeze shouldn't be allowed. -George