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Re: [Xen-devel] iommu=0 leading to panic when system defaults to using x2apic
- To: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>
- From: Keir Fraser <keir@xxxxxxx>
- Date: Fri, 10 Dec 2010 18:49:46 +0000
- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Han, Weidong" <weidong.han@xxxxxxxxx>
- Delivery-date: Fri, 10 Dec 2010 10:52:27 -0800
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- Thread-topic: [Xen-devel] iommu=0 leading to panic when system defaults to using x2apic
Ah, and the interrupt remapping dependency is because PCI(e) devices cannot
address 32-bit APIC IDs?
On 10/12/2010 18:26, "Kay, Allen M" <allen.m.kay@xxxxxxxxx> 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.
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Jan Beulich
> Sent: Friday, December 10, 2010 7:40 AM
> To: Zhang, Yang Z
> Cc: Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx; 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" <yang.z.zhang@xxxxxxxxx> 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
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