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RE: [Xen-devel] x2apic mode vs. interrupt remapping

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: RE: [Xen-devel] x2apic mode vs. interrupt remapping
From: "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>
Date: Wed, 3 Mar 2010 22:09:12 +0800
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Thread-topic: [Xen-devel] x2apic mode vs. interrupt remapping
When iommu_supports_eim is called in enable_x2apic, drhd is already parsed in 
acpi_boot_init, so iommu_supports_eim should return hardware's real capability. 
That is to say, if eim is no supported on platform, x2apic shouldn't be enabled 
at all. 

Jan Beulich wrote:
>>>> "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx> 03.03.10 14:32 >>>
>> According to the #Cset20168, x2apic is only enabled when all VT-d
>> engines support IR and EIM support, so the policy should be same
>> with Linux's.
> I would say that c/s has the intended behavior you describe, but since
> iommu_setup() runs after enable_x2apic(), the call to
> iommu_supports_eim() still returns true (iommu_enabled, iommu_qinval,
> and iommu_inremap all have an initial value of 1, and with no drhd
> present the function returns 1.
> Jan

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