[PATCH v2 0/4] irqchip: GICv2/v3: Add support for irq_vcpu_affinity

[Marc Zyngier]

The GICv2 and GICv3 architectures allow an active physical interrupt
to be forwarded to a guest, and the guest to indirectly perform the
deactivation of the interrupt by performing an EOI on the virtual
interrupt (see for example the GICv2 spec, 3.2.1).

This allows some substantial performance improvement for level
triggered interrupts that otherwise have to be masked/unmasked in
VFIO, not to mention the required trap back to KVM when the guest
performs an EOI.

To enable this, the GICs need to be switched to a different EOImode,
where a taken interrupt can be left "active" (which prevents the same
interrupt from being taken again), while other interrupts are still
being processed normally.

We also use the new irq_set_vcpu_affinity hook that was introduced for
Intel's "Posted Interrupts" to determine whether or not to perform the
deactivation at EOI-time.

As all of this only makes sense when the kernel can behave as a
hypervisor, we only enable this mode on detecting that the kernel was
actually booted in HYP mode, and that the GIC supports this feature.

This series is a complete rework of a RFC I sent over a year ago:

http://lists.infradead.org/pipermail/linux-arm-kernel/2014-June/266328.html

Since then, a lot has been either merged (the irqchip_state) or reworked
(my active-timer series: http://www.spinics.net/lists/kvm/msg118768.html),
and this implements the last few bits for Eric Auger's series to
finally make it into the kernel:

https://lkml.org/lkml/2015/7/2/268
https://lkml.org/lkml/2015/7/6/291

With all these patches combined, physical interrupt routing from the
kernel into a VM becomes possible.

This has been tested on Juno (GICv2) and FastModel (GICv3). A branch
is available at:

git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/gic-irq-vcpu-affinity-v2

* From v1:
  - Fixes after review from Eric
  - Got rid of the cascaded GICv2 hack (it was broken anyway)
  - Folded the LPI deactivation patch (it makes more sense as part of
    the main one.
  - Some clarifying comments about the "deactivate on mask"
  - I haven't retained Eric's Reviewed/Tested-by, as the code as
    significantly changed on GICv2

Marc Zyngier (4):
  irqchip: GICv3: Convert to EOImode == 1
  irqchip: GICv3: Don't deactivate interrupts forwarded to a guest
  irqchip: GIC: Convert to EOImode == 1
  irqchip: GIC: Don't deactivate interrupts forwarded to a guest

 drivers/irqchip/irq-gic-v3.c       |  68 +++++++++++++++++++++--
 drivers/irqchip/irq-gic.c          | 109 ++++++++++++++++++++++++++++++++++++-
 include/linux/irqchip/arm-gic-v3.h |   9 +++
 include/linux/irqchip/arm-gic.h    |   4 ++
 4 files changed, 184 insertions(+), 6 deletions(-)

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2.1.4