FROMLIST: irqchip/gic-v3-its: Mark some in-memory data structures as 'decrypted'

The GICv3 ITS driver allocates memory for its tables using alloc_pages()
and performs explicit cache maintenance if necessary. On systems such
as those running pKVM, where the memory encryption API is implemented,
memory shared with the ITS must first be transitioned to the "decrypted"
state, as it would be if allocated via the DMA API.

Allow pKVM guests to interact with an ITS emulation by ensuring that the
shared pages are decrypted at the point of allocation and encrypted
again upon free().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20211208155916.681-1-will@kernel.org


Bug: 209580772
Change-Id: I89820c65769a07306fd3e067d7d33c938d156820
Signed-off-by: Quentin Perret <qperret@google.com>