From mboxrd@z Thu Jan 1 00:00:00 1970 From: Weidong Han Subject: Re: [PATCH] VT-d: improve RMRR validity checking Date: Wed, 10 Mar 2010 10:40:51 +0800 Message-ID: <4B9706B3.3050903@intel.com> References: <4B59098B.6000108@intel.com> <4B590FA4.4000008@jp.fujitsu.com> <4B59132B.40607@intel.com> <4B59188C.50901@jp.fujitsu.com> <4B59660F.4000909@intel.com> <7162ab21003091339i4adb8669safd5e074607386a2@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <7162ab21003091339i4adb8669safd5e074607386a2@mail.gmail.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Alex Williamson Cc: "xen-devel@lists.xensource.com" , Noboru Iwamatsu , "Cihula, Joseph" , "Kay, Allen M" , "linux@eikelenboom.it" , "keir.fraser@eu.citrix.com" List-Id: xen-devel@lists.xenproject.org Alex Williamson wrote: > On Fri, Jan 22, 2010 at 1:47 AM, Weidong Han wrote: > >> I implemented a patch and attached. >> >> patch description: >> In order to make Xen more defensive to VT-d related BIOS issue, this patch >> ignores a DRHD if all devices under its scope are not pci discoverable, and >> regards a DRHD as invalid and then disable whole VT-d if some devices under >> its scope are not pci discoverable. But if iommu=force is set, it will >> enable all DRHDs reported by BIOS, to avoid any security vulnerability with >> malicious s/s re-enabling "supposed disabled" devices. Pls note that we >> don't know the devices under the "Include_all" DRHD are existent or not, >> because the scope of "Include_all" DRHD won't enumerate common pci device, >> it only enumerates I/OxAPIC and HPET devices. >> > > Hi All, > > I have a system with what I consider to be a valid DRHD that's getting > tripped up on this patch. The problem is that the DRHD includes an > IOAPIC scope, where the IOAPIC is not materialized on the PCI bus. I > think Xen is being overzealous in it's validity checking and that this > is a valid configuration. What do others think? Are IOAPICs a > special case that we can allow to be non-existent on the PCI bus? > Yes, IOAPIC can be not pci-discoverable. IOAPICs are only reported in the "Include_all" DRHD, and our patch won't check if the device is pci-discoverable or not for the "Include_all" DRHD. So I think the patch is no problem unless IOAPIC is not included in the "Include_all" DRHD. Can you post your boot logs? Regards, Weidong > Thanks, > > Alex >