[Xen-devel] [PATCH 0 of 4] interrupt remapping in HVM guests

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

Hi all,
this patch series implements the mechanisms needed by a PV on HVM guest
to remap interrupts and MSIs into pirqs in order to receive those
interrupts and MSIs as xen events.
This allows the guest to avoid any reads and writes to the emulated
LAPIC.
The series consists of 4 patches, 2 patches for the hypervisor and 2
patches to qemu-xen; the changes are not interdependent.

Xen needs to export some pirq related physdev_op hypercalls to hvm
guests and keep track of all the remapped interrupts, that can either be
interrupts corresponding to emulated devices or passthrough devices.
A new physdev_op hypercall has been added to export the number of pirq
available: considering that the guest is allowed to choose the pirq
number, we can make sure the number it chooses is in the allowed range.
The first patch to qemu-xen is to support MSI remapping: in order to remap
an MSI into a pirq the guest enables the MSI passing 0 as vector number,
in response qemu-xen reads the address and use it a pirq number for the
following mapping request to xen.
Finally we avoid pirq conclicts letting xen pick the pirq number for us
in qemu-xen.

The list of patches follows:

xen: interrupt remapping in HVM guests
xen: introduce PHYSDEVOP_get_nr_pirqs
qemu-xen: support PV on HVM MSI remapping
qemu-xen: qemu-xen: let xen choose the pirq number

Cheers,

Stefano Stabellini

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