[Xen-devel] Re: [PATCH][VTD] force boot to fail if interrupt rem

To:	"Kay, Allen M" <allen.m.kay@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject:	[Xen-devel] Re: [PATCH][VTD] force boot to fail if interrupt remapping cannot be enabled when iommu=force
From:	Keir Fraser <keir.xen@xxxxxxxxx>
Date:	Thu, 28 Apr 2011 18:05:03 +0100
Cc:	"Cihula, Joseph" <joseph.cihula@xxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
Delivery-date:	Thu, 28 Apr 2011 10:06:05 -0700
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On 28/04/2011 00:42, "Kay, Allen M" <allen.m.kay@xxxxxxxxx> wrote:

> Force Xen boot to fail if interrupt remapping fails to enable and the
> following are true: iommu=force is set as xen boot parameter, VT-d engine HW
> is interrupt remapping capable, DMAR_INTR_REMAP bit is set in DMAR flags.
> This forces iommu=force boot instances has interrupt remapping enabled if HW
> and BIOS supports it.

If HW and BIOS support it, why would it fail to be enabled? This doesn't
look like a particularly useful panic() path. If interrupt remapping is so
important, perhaps iommu=force should unconditionally require it, and panic
in its absence regardless of platform features? As it is, this looks like a
panic that is never realistically going to trigger.

 -- Keir

> Signed-off-by: Allen Kay <allen.m.kay@xxxxxxxxx>

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