KVM: arm64: Fix range alignment when walking page tables

When walking the page tables at a given level, and if the start
address for the range isn't aligned for that level, we propagate
the misalignment on each iteration at that level.

This results in the walker ignoring a number of entries (depending
on the original misalignment) on each subsequent iteration.

Properly aligning the address before the next iteration addresses
this issue.

Cc: stable@vger.kernel.org
Reported-by: NHoward Zhang <Howard.Zhang@arm.com>
Acked-by: NWill Deacon <will@kernel.org>
Signed-off-by: NJia He <justin.he@arm.com>
Fixes: b1e57de6 ("KVM: arm64: Add stand-alone page-table walker infrastructure")
[maz: rewrite commit message]
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210303024225.2591-1-justin.he@arm.com
Message-Id: <20210305185254.3730990-9-maz@kernel.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/arm64/kvm/hyp/pgtable.c

@@ -223,6 +223,7 @@ static inline int __kvm_pgtable_visit(struct kvm_pgtable_walk_data *data,
 		goto out;
 
 	if (!table) {
+		data->addr = ALIGN_DOWN(data->addr, kvm_granule_size(level));
 		data->addr += kvm_granule_size(level);
 		goto out;
 	}