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SubjectRE: [PATCH V6 2/3] IOMMU/Hyper-V: Add Hyper-V stub IOMMU driver
From: <> Sent: Wednesday, February 27, 2019 6:54 AM
> On the bare metal, enabling X2APIC mode requires interrupt remapping
> function which helps to deliver irq to cpu with 32-bit APIC ID.
> Hyper-V doesn't provide interrupt remapping function so far and Hyper-V
> MSI protocol already supports to deliver interrupt to the CPU whose
> virtual processor index is more than 255. IO-APIC interrupt still has
> 8-bit APIC ID limitation.
> This patch is to add Hyper-V stub IOMMU driver in order to enable
> X2APIC mode successfully in Hyper-V Linux guest. The driver returns X2APIC
> interrupt remapping capability when X2APIC mode is available. Otherwise,
> it creates a Hyper-V irq domain to limit IO-APIC interrupts' affinity
> and make sure cpus assigned with IO-APIC interrupt have 8-bit APIC ID.
> Define 24 IO-APIC remapping entries because Hyper-V only expose one
> single IO-APIC and one IO-APIC has 24 pins according IO-APIC spec(
> Reviewed-by: Michael Kelley <>
> Signed-off-by: Lan Tianyu <>

Reconfirming my reviewed-by after the change to fix the
compile error detected by the kbuild test robot.

Reviewed-by: Michael Kelley <>

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