KVM: arm64: Top up the memcache for pKVM permission faults

A permission fault normally only relaxes a leaf, so user_mem_abort()
skips the memcache top-up. Under pKVM such a fault can instead collapse
pages into a block. That needs a fresh pkvm_mapping object, and without
it cache->mapping is NULL, so pkvm_pgtable_stage2_map() dereferences NULL
and faults the host under mmu_lock. Staging only the object is not
enough: the hypervisor requires kvm_mmu_cache_min_pages in the memcache
even for the allocation-free install, so under memcache pressure the
collapse returns -ENOMEM and trips the WARN_ON(ret) in
pkvm_pgtable_stage2_map() where a non-pKVM guest succeeds.

Top up the full memcache for pKVM permission faults so both the mapping
object and the min-pages are staged before mmu_lock.

Fixes: db14091d8f75 ("KVM: arm64: Stage-2 huge mappings for np-guests")
Reported-by: Bradley Morgan <include@grrlz.net>
Link: https://lore.kernel.org/all/20260623161545.EA08E1F000E9@smtp.kernel.org/
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Tested-by: Bradley Morgan <include@grrlz.net> # On pixel 7, Android 17 CP2A.260705.006
Test: Bradley Morgan <include@grrlz.net> # On QEMU arm64 host
Link: https://patch.msgid.link/20260717130317.1953574-3-fuad.tabba@linux.dev
Signed-off-by: Oliver Upton <oupton@kernel.org>

0 files changed, 0 insertions, 0 deletions