From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: lapic & npt Date: Fri, 06 Jun 2008 19:30:23 +0300 Message-ID: <4849661F.2050908@qumranet.com> References: <4846BEB8.1000208@redhat.com> <4846BFE0.8070507@qumranet.com> <48494D82.4030803@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Gerd Hoffmann Return-path: Received: from il.qumranet.com ([212.179.150.194]:37388 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752938AbYFFQaT (ORCPT ); Fri, 6 Jun 2008 12:30:19 -0400 In-Reply-To: <48494D82.4030803@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Gerd Hoffmann wrote: > Avi Kivity wrote: > >> Gerd Hoffmann wrote: >> >>> Hi, >>> >>> I've just noticed that xenner doesn't work for 64bit xen guest kernels >>> on my new shiny barcelona box. The VM crashes when trying to access the >>> lapic. lapic setup is done before idt setup, register dump looks like >>> init state, thus it most likely is a triple fault resetting the vcpu. >>> Turning off npt fixes it. >>> >>> xenner maps the lapic to ffff820000000000 (64bit guests) or fe900000 >>> (32bit guests). 32bit works fine even with npt enabled. >>> >>> host kernel is fedora 9 with kvm-69 modules. >>> >>> ideas anyone? >>> >> Turn on logging in lapic.c. See if something turns up. >> >> If not, the page tables are probably set up incorrectly, but in a way >> that kvm doesn't notice. >> > > Figured meanwhile the instruction accessing the lapic register somehow > beames me into my gpf handler. With a quite strange rsp value. Hmm. > To be analyzed further after kvm forum I guess, unless someone has a > bright idea ... > x86-64 will gpf if an address is not canonical. ffff820000000000 is canonical, but perhaps a type killed a zero somewhere? -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.