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Re: [Xen-devel] iommu=0 leading to panic when system defaults to using x

To: Jan Beulich <JBeulich@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] iommu=0 leading to panic when system defaults to using x2apic
From: Keir Fraser <keir@xxxxxxx>
Date: Fri, 10 Dec 2010 10:06:53 +0000
Cc:
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Thread-topic: [Xen-devel] iommu=0 leading to panic when system defaults to using x2apic
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Are you looking at xen-4.0? I think you should look at latest xen-unstable
and we can backpoprt patches if that is more satisfactory. I did a big
cleanup patch yesterday which makes the code smaller and clearer than it
was, yet I don't understand the dependencies between x2apic-enabled-by-bios
and the need for interrupt remapping, and all that stuff.

 -- Keir

On 10/12/2010 09:12, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:

> Why wouldn't iommu=0 imply not using the x2apic, if use of the
> iommu indeed is a prerequisite (which by itself seems questionable
> as long as APIC IDs aren't wider than 8 bits)?
> 
> Looking further at enable_bsp_x2apic(), I also wonder whether
> the pre-enabled case, when specifying iommu=0 and x2apic=0,
> can actually work if iommu=0 is a prerequisite (intremap_enabled()
> would return 1 in that case afaics, so the early check doesn't help).
> 
> Thanks, Jan
> 
> 
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