The zap_vma_ptes() is declared but not defined on NOMMU kernels, causing a link error for the newly added uverbs code: drivers/infiniband/core/uverbs_main.o: In function `uverbs_user_mmap_disassociate': uverbs_main.c:(.text+0x114c): undefined reference to `zap_vma_ptes' drivers/infiniband/core/uverbs_main.o: In function `rdma_umap_open': uverbs_main.c:(.text+0x53c): undefined reference to `zap_vma_ptes' To fix this, we can either make uverbs depend on CONFIG_MMU, or try to build it anyway. Since this is the only compile-time dependency, I decided to allow building it with an extra compile-time check for CONFIG_MMU before calling the one function. Fixes: 5f9794dc94f5 ("RDMA/ucontext: Add a core API for mmaping driver IO memory") Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> --- drivers/infiniband/core/uverbs_main.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c index 40dcf3d02a4b..5c1202af0748 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -884,7 +884,8 @@ static void rdma_umap_open(struct vm_area_struct *vma) * point, so zap it. */ vma->vm_private_data = NULL; - zap_vma_ptes(vma, vma->vm_start, vma->vm_end - vma->vm_start); + if (IS_ENABLED(CONFIG_MMU)) + zap_vma_ptes(vma, vma->vm_start, vma->vm_end - vma->vm_start); } static void rdma_umap_close(struct vm_area_struct *vma) @@ -1023,8 +1024,9 @@ void uverbs_user_mmap_disassociate(struct ib_uverbs_file *ufile) continue; list_del_init(&priv->list); - zap_vma_ptes(vma, vma->vm_start, - vma->vm_end - vma->vm_start); + if (IS_ENABLED(CONFIG_MMU)) + zap_vma_ptes(vma, vma->vm_start, + vma->vm_end - vma->vm_start); vma->vm_flags &= ~(VM_SHARED | VM_MAYSHARE); } mutex_unlock(&ufile->umap_lock); -- 2.18.0