<html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#FFFFFF" text="#000000"> <div class="moz-cite-prefix">Am 12.07.2012 00:38, schrieb Eric Blake: </div> <blockquote cite="mid:4FFE0080.7050200@redhat.com" type="cite"> This may be the result of a security fix in the new kernel. I know at least one older version of Intel chips has a bug where IOMMU can be exploited by a guest to take control over the host, so on those chips, newer kernels now require to explicitly enable a kernel module parameter to state that you are going to allow passthrough to the guest in spite of the security risk. That is, you may need to use: modprobe kvm allow_unsafe_assigned_interrupts=1 with your newer kernel. Unfortunately, I wasn't able to find a better URL to a page documenting this issue, so that implies we probably also need a patch to the libvirt documentation with regards to using device passthrough. </blockquote> Hi Eric, thanks for the info. Reading <meta http-equiv="content-type" content="text/html; charset=ISO-8859-1"> <a href="https://bugzilla.redhat.com/show_bug.cgi?id=715555">https://bugzilla.redhat.com/show_bug.cgi?id=715555</a> , it seems that 5.8 shouldn't be affected since the kvm on that version doesn't support interrupt remapping, if I understand correctly. Additionally, if I run the script provided in the issue description, the check passes with "Interrupt remapping support available" and the error message differs: I don't get "Operation not permitted" but "Invalid argument". I also can't set provides switch in /sys/module/kvm/parameters/allow_unsafe_assigned_interrupts, since the file isn't there on my box. Are there any other circumstances where pci passthrough could fail? Googling for the error message i get, I can't seem to find any case that matches mine. This makes me guess that I'd rather accidentally introduced a misconfiguration than encountered a qemu-kvm/libvirt bug. I have attached the configuration file of that machine, maybe someone could have a look at the hostdev section? Unfortunately, i am currently not able to switch back to the prior kernel, since the system is in production right now - I will test that later during the day. Thanks & cheers, Rouven <pre class="moz-signature" cols="72">-- Blinkenlichten Open Source Solutions Maass Sacha GbR | Weigandufer 45 | 12059 Berlin tel: +493013896247 | fax: +493013896249 | mob: +491744220127 Web: <a class="moz-txt-link-freetext" href="http://www.blinkenlichten.de/">http://www.blinkenlichten.de/</a> G+: <a class="moz-txt-link-freetext" href="http://gplus.to/blinkenlichten">http://gplus.to/blinkenlichten</a> Blinkenlichten Zarafa Hosted Tweets: <a class="moz-txt-link-freetext" href="http://twitter.com/zarafamail/">http://twitter.com/zarafamail/</a> </pre> </body> </html>