KVM: selftests: Mark correct page as mapped in virt_map()

The loop marks vaddr as mapped after incrementing it by page size,
thereby marking the *next* page as mapped. Set the bit in vpages_mapped
first instead.

Fixes: 56fc7732 ("KVM: selftests: Fill in vm->vpages_mapped bitmap in virt_map() too")
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Message-Id: <20221209015307.1781352-4-oliver.upton@linux.dev>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/lib/kvm_util.c

@@ -1425,10 +1425,10 @@ void virt_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr,
 
 	while (npages--) {
 		virt_pg_map(vm, vaddr, paddr);
+		sparsebit_set(vm->vpages_mapped, vaddr >> vm->page_shift);
+
 		vaddr += page_size;
 		paddr += page_size;
-
-		sparsebit_set(vm->vpages_mapped, vaddr >> vm->page_shift);
 	}
 }