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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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.