KVM: arm64: Add a heap allocator for the pKVM hyp

Currently, memory used by the hypervisor comes from donations that are
embedded within HVCs. e.g. __pkvm_init_vm()'s hyp_vm.

This is cumbersome: the host needs to know the size of those
struct, the memory must be page-aligned and physically contiguous which
may be difficult to satisfy when host memory is highly fragmented.

Create a heap allocator to manage VA-contiguous memory. This allocator
grows upward, recycles unused chunks of memory and provides a simple API
to allocate and free:

  hyp_alloc(size), hyp_free(addr)

This heap allocator also manages the underlying physical memory,
allowing the host to top up the allocator's pool and reclaim memory.

  hyp_alloc_topup(), hyp_alloc_reclaim().

Pages remain mapped in the allocator's VA-space as long as they are not
reclaimed.

When the allocator runs out of memory, hyp_alloc() fails and
hyp_alloc_errno() returns -ENOMEM to signal that a top-up is required.

Additionally, harden the allocator with a fast hash of the chunks
meta-data. This intends to detect accidental corruptions and makes the
allocator slightly more robust to potential attacks.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Tested-by: Fuad Tabba <fuad.tabba@linux.dev>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20261001142849.3367614-5-vdonnefort@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>

0 files changed, 0 insertions, 0 deletions