From mboxrd@z Thu Jan 1 00:00:00 1970 From: Noboru Iwamatsu Subject: Re: [PATCH] VT-d: improve RMRR validity checking Date: Fri, 22 Jan 2010 11:38:28 +0900 Message-ID: <4B590FA4.4000008@jp.fujitsu.com> References: <4B59098B.6000108@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4B59098B.6000108@intel.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: weidong.han@intel.com Cc: xen-devel@lists.xensource.com, linux@eikelenboom.it, joseph.cihula@intel.com, keir.fraser@eu.citrix.com List-Id: xen-devel@lists.xenproject.org Hi Weidong, I'm not sure why the security problem is caused by ignoring the DRHD that has only non-existent devices. Could you explain details or where to read the spec? As you saying, security is the top-priority. However, when iommu=force is specified, we should enable vt-d if there are some potential issues. Because users want to "force" anyway. Regards, Noboru. > Keir Fraser wrote: >> If we want to keep iommu=1 as default, then it is unacceptable to fail to >> boot on a fairly wide range of modern systems. We have to >> warn-and-disable, >> partially or completely, unless iommu=force is specified. Or we need to >> revert to iommu=0 as the default. >> >> What do you think, Weidong? > Yes. I agree to warn-and-disable for these BIOS issues, and consider > security more when iommu=force. Therefore I will implement a patch based > on Nororu's patch. > > Regards, > Weidong > >> -- Keir >> >> On 21/01/2010 14:17, "Sander Eikelenboom" wrote: >> >>> Hello Weidong, >>> >>> The problem is most vendor's just don't fix it and ignore the problem >>> completely. >>> Most often hiding them selves behind: come back when it's a problem with >>> Microsoft Windows, that the only single thing we support (and no other >>> software, so no vmware, no xen, no linux, perhaps even no hypervisor) >>> Well I don't know if the virtual pc in windows 7 supports an iommu >>> now, but it >>> didn't in the past as far as i know, so any complain bounces off, and >>> there it >>> all seems to end for them. >>> >>> Besides that i don't know if they do know what the problems with there >>> implementation in BIOS is when someone reports it. >>> I think some behind the scenes pressure from Intel to vendors might >>> help to >>> solve some of them. >>> (my Q35 chipset, "Intel V-PRO" marketed motherboard (so much for >>> that) also >>> suffers RMRR problem when another graphics card is inserted which >>> switches off >>> the IGD). >>> >>> Although i think in my case your patch will work around that for me. >>> Perhaps a >>> third option is needed, which does all the workarounds possible and >>> warns >>> about potential security problem when requested ? >>> >>> -- >>> Sander >>> >>> >>> >>> >>> >>> >>> Thursday, January 21, 2010, 1:46:39 PM, you wrote: >>> >>>> Noboru Iwamatsu wrote: >>>>> Hi Weidong, >>>>> >>>>> I re-send the DRHD-fix patch. >>>>> >>>>> If DRHD does not have existent devices, ignore it. >>>>> If DRHD has both existent and non-existent devices, consider it >>>>> invalid >>>>> and not register. >>>> Although you patch workarounds your buggy BIOS, but we still need to >>>> enable it for security purpose as I mentioned in previous mail. We >>>> needn't workaround / fix all BIOS issues in software. I think security >>>> is more important for this specific BIOS issue. Did you report the BIOS >>>> issue to your OEM vendor? maybe it's better to get it fixed in BIOS. >>>> Regards, >>>> Weidong >>>>> According to this patch and yours, my machine successfully booted >>>>> with vt-d enabled. >>>>> >>>>> Signed-off-by: Noboru Iwamatsu >>>>> >>>>> >>>>>> Keir Fraser wrote: >>>>>>> On 21/01/2010 10:19, "Weidong Han" wrote: >>>>>>> >>>>>>>>> Sorry this is typo. >>>>>>>>> I mean: >>>>>>>>> So, I think RMRR that has no-existent device is "invalid" >>>>>>>>> and whole RMRR should be ignored. >>>>>>>> looks reasonable. >>>>>>>> >>>>>>>> Keir, I Acks Noboru's rmrr patch. Or do you want us to merge >>>>>>>> them to one >>>>>>>> patch? >>>>>>> Merge them up, re-send with both sign-off and acked-by all in one >>>>>>> email. >>>>>>> >>>>>>> Thanks, >>>>>>> Keir >>>>>>> >>>>>> Sorry, I disagree with Noboru after thinking it again. If the RMRR >>>>>> has >>>>>> both no-existent device and also has existent devices in its >>>>>> scope, we >>>>>> should not ignore it because the existent devices under its scope >>>>>> will >>>>>> be impacted without the RMRR. so I suggest to print a warning >>>>>> instead of >>>>>> ignore it. Attached a patch for it. >>>>>> >>>>>> Signed-off-by: Weidong Han >>> >>> >>> >> >> >