From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: iommu=0 leading to panic when system defaults to using x2apic Date: Fri, 10 Dec 2010 18:49:46 +0000 Message-ID: References: <987664A83D2D224EAE907B061CE93D530193BB9EB8@orsmsx505.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <987664A83D2D224EAE907B061CE93D530193BB9EB8@orsmsx505.amr.corp.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: "Kay, Allen M" , Jan Beulich , "Zhang, Yang Z" Cc: "xen-devel@lists.xensource.com" , "Han, Weidong" List-Id: xen-devel@lists.xenproject.org Ah, and the interrupt remapping dependency is because PCI(e) devices cannot address 32-bit APIC IDs? -- Keir On 10/12/2010 18:26, "Kay, Allen M" wrote: > The architectural requirement is actually between interrupt remapping and > x2apic. Since interrupt remapping is part of the VT-d feature so current > software requires all VT-d features enabled in order for x2apic to be enabled. > > Strictly speaking DMA remapping is not required for x2apic. However, queued > invalidation is required since interrupt remapping requires queued > invalidation. So x2apic dependency is as follows: > > x2apic->interrupt remapping->queued invalidation > > Due to historical reasons, the new VT-d features were built on top of the old > ones as they become available. Is there a requirement to separate this out? > If so, we will need to re-design iommu boot parameter which took a while to > get it right so most systems can now boot successfully. > > Allen > > -----Original Message----- > From: xen-devel-bounces@lists.xensource.com > [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Jan Beulich > Sent: Friday, December 10, 2010 7:40 AM > To: Zhang, Yang Z > Cc: Keir Fraser; xen-devel@lists.xensource.com; Han, Weidong > Subject: RE: [Xen-devel] iommu=0 leading to panic when system defaults to > using x2apic > >>>> On 10.12.10 at 16:00, "Zhang, Yang Z" wrote: >> Yes, X2apic is depend on iommu. If disable iommu when using x2apic, it will >> trigger the panic. > > Would mind clarifying where this dependency actually is? > > Thanks, Jan > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel