[PATCH 30/89] KVM: arm64: Do not allow memslot changes after first VM run under pKVM

[Will Deacon]

From: Fuad Tabba <tabba at google.com>

As the guest stage-2 page-tables will soon be managed entirely by EL2
when pKVM is enabled, guest memory will be pinned and the MMU notifiers
in the host will be unable to reconfigure mappings at EL2 other than
destrroying the guest and reclaiming all of the memory.

Forbid memslot move/delete operations for VMs that have run under pKVM,
returning -EPERM to userspace if such an operation is requested.

Signed-off-by: Fuad Tabba <tabba at google.com>
---
 arch/arm64/kvm/mmu.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 0071f035dde8..67cac3340d49 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1679,6 +1679,13 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	hva_t hva, reg_end;
 	int ret = 0;
 
+	/* In protected mode, cannot modify memslots once a VM has run. */
+	if (is_protected_kvm_enabled() &&
+	    (change == KVM_MR_DELETE || change == KVM_MR_MOVE) &&
+	    kvm->arch.pkvm.shadow_handle) {
+		return -EPERM;
+	}
+
 	if (change != KVM_MR_CREATE && change != KVM_MR_MOVE &&
 			change != KVM_MR_FLAGS_ONLY)
 		return 0;
@@ -1755,6 +1762,10 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
 	gpa_t gpa = slot->base_gfn << PAGE_SHIFT;
 	phys_addr_t size = slot->npages << PAGE_SHIFT;
 
+	/* Stage-2 is managed by hyp in protected mode. */
+	if (is_protected_kvm_enabled())
+		return;
+
 	write_lock(&kvm->mmu_lock);
 	unmap_stage2_range(&kvm->arch.mmu, gpa, size);
 	write_unlock(&kvm->mmu_lock);
-- 
2.36.1.124.g0e6072fb45-goog