iommu/hyper-v: Add Hyper-V stub IOMMU driver
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(
https://pdos.csail.mit.edu/6.828/2016/readings/ia32/ioapic.pdf).
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index d9a2571..34b0665 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -435,4 +435,13 @@
help
Support for IOMMU on certain Qualcomm SoCs.
+config HYPERV_IOMMU
+ bool "Hyper-V x2APIC IRQ Handling"
+ depends on HYPERV
+ select IOMMU_API
+ default HYPERV
+ help
+ Stub IOMMU driver to handle IRQs as to allow Hyper-V Linux
+ guests to run with x2APIC mode enabled.
+
endif # IOMMU_SUPPORT