[RFC PATCH v1 4/9] KVM: arm64: Skip VMA checks for slots without userspace address

[Fuad Tabba <tabba@google.com>]

Memory slots backed by guest memory might be created with no
intention of being mapped by the host. These are recognized by
not having a userspace address in the memory slot.

VMA checks are neither possible nor necessary for this kind of
slot, so skip them.

Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/arm64/kvm/mmu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index c9d46ad57e52..342a9bd3848f 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -988,6 +988,10 @@ static void stage2_unmap_memslot(struct kvm *kvm,
 	phys_addr_t size = PAGE_SIZE * memslot->npages;
 	hva_t reg_end = hva + size;
 
+	/* Host will not map this private memory without a userspace address. */
+	if (kvm_slot_can_be_private(memslot) && !hva)
+		return;
+
 	/*
 	 * A memory region could potentially cover multiple VMAs, and any holes
 	 * between them, so iterate over all of them to find out if we should
@@ -2133,6 +2137,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	hva = new->userspace_addr;
 	reg_end = hva + (new->npages << PAGE_SHIFT);
 
+	/* Host will not map this private memory without a userspace address. */
+	if ((kvm_slot_can_be_private(new)) && !hva)
+		return 0;
+
 	mmap_read_lock(current->mm);
 	/*
 	 * A memory region could potentially cover multiple VMAs, and any holes
-- 
2.48.0.rc2.279.g1de40edade-goog