arm64: KVM: Add support for VPIPT I-caches

arm64: KVM: Add support for VPIPT I-caches

A VPIPT I-cache has two main properties:

1. Lines allocated into the cache are tagged by VMID and a lookup can
   only hit lines that were allocated with the current VMID.

2. I-cache invalidation from EL1/0 only invalidates lines that match the
   current VMID of the CPU doing the invalidation.

This can cause issues with non-VHE configurations, where the host runs
at EL1 and wants to invalidate I-cache entries for a guest running with
a different VMID. VHE is not affected, because the host runs at EL2 and
I-cache invalidation applies as expected.

This patch solves the problem by invalidating the I-cache when unmapping
a page at stage 2 on a system with a VPIPT I-cache but not running with
VHE enabled. Hopefully this is an obscure enough configuration that the
overhead isn't anything to worry about, although it does mean that the
by-range I-cache invalidation currently performed when mapping at stage
2 can be elided on such systems, because the I-cache will be clean for
the guest VMID following a rollover event.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>