So far, we map all VPEs on all ITSs. While this is not wrong,
this is quite a big hammer, as moving a VPE around requires
all ITSs to be synchronized. Needles to say, this is an
expensive proposition.

Instead, let's switch to a mode where we issue VMAPP commands
only on ITSs that are actually involved in reporting interrupts
to the given VM.

For that purpose, we refcount the number of interrupts are are
mapped for this VM on each ITS, performing the map/unmap
operations as required. It then allows us to use this refcount
to only issue VMOVP to the ITSs that need to know about this
VM.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

As we're about to make use of the maximum number of ITSs in
a GICv4 system, let's make this value global (and rename it to
GICv4_ITS_LIST_MAX).
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Get the show on the road...
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Add the required interfaces to map, unmap and update a VLPI.
Reviewed-by: NEric Auger <eric.auger@redhat.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Add the required interfaces to schedule a VPE and perform a
VINVALL command.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NEric Auger <eric.auger@redhat.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

When creating a VM, it is very convenient to have an irq domain
containing all the doorbell interrupts associated with that VM
(each interrupt representing a VPE).
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

When we don't have the DirectLPI feature, we must work around the
architecture shortcomings to be able to perform the required
maintenance (interrupt masking, clearing and injection).

For this, we create a fake device whose sole purpose is to
provide a way to issue commands as if we were dealing with LPIs
coming from that device (while they actually originate from
the ITS). This fake device doesn't have LPIs allocated to it,
but instead uses the VPE LPIs.

Of course, this could be a real bottleneck, and a naive
implementation would require 6 commands to issue an invalidation.

Instead, let's allocate at least one event per physical CPU
(rounded up to the next power of 2), and opportunistically
map the VPE doorbell to an event. This doorbell will be mapped
until we roll over and need to reallocate this slot.

This ensures that most of the time, we only need 2 commands
to issue an INV, INT or CLEAR, making the performance a lot
better, given that we always issue a CLEAR on entry, and
an INV on each side of a trapped WFI.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

Add a bunch of GICv4-specific data structures that will get used in
subsequent patches.
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>