KVM: arm64: gic-v5: Create and manage VM and VPE tables

GICv5 uses a set of in-memory tables to track and manage VM state.
These must be allocated by the hypervisor and provided to the IRS.

The VMT (Virtual Machine Table) is a linear or two-level table
comprising VMT Entries (VMTEs). Each VMTE describes the state for a
single VM. This state includes things such as the SPI and LPI IST
configuration (coming in a future commit), an implementation-defined
VM Descriptor, and a VPE Table (VPET).

The VPET contains one entry per possible VPE ID belonging to a VM. It
is used to mark a VPE as valid and provide the address of an
implementation-defined VPE Descriptor (VPED), which the hardware uses
to track and manage VPE state.

Allocate each VM's VPEDs as a single dense array indexed by vcpu_idx,
while the VPET remains indexed by the userspace-provided vcpu_id. This
keeps VPED storage proportional to the number of vCPUs even when their
IDs are sparse.

The VMT and VPET are shared with the IRS. On systems with a
non-coherent IRS, cache maintenance operates at cache-line
granularity, while multiple entries can occupy the same cache line.
Use a common lock for CPU accesses to these tables and IRS command
processing so that writing back one entry cannot overwrite an IRS
update to a neighbouring entry.

The implementation-defined VMD and VPED storage is also visible to the
IRS. Round these allocations up to whole cache lines to prevent cache
maintenance from corrupting unrelated slab objects. Initialise the
storage before publishing its addresses to the IRS.

This commit adds support for allocating the VMT and its descriptor
backing state, and for managing VMTEs. The VMTEs can be initialised or
released for reuse. VM IDs are allocated with an IDA, while an XArray
tracks the host-side allocations associated with populated VMTEs.

Signed-off-by: Sascha Bischoff <sascha.bischoff@arm.com>
Link: https://patch.msgid.link/20260904113404.4051341-10-sascha.bischoff@arm.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

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