Skip to contentSkip to conversation

RDMA/ucontext: fix building with CONFIG_MMU=n

PATCH In review Arnd Bergmann 2 participants 3 messages Sep 27, 2018 – Sep 28, 2018 InfiniBand

lore
Share & tools
lore

Arnd Bergmann

author
#0 lore raw

PATCH 1/1 RDMA/ucontext: fix building with CONFIG_MMU=n

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 <[email protected]>
---
 drivers/infiniband/core/uverbs_main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
drivers/infiniband/core/uverbs_main.c +5 -3
index 40dcf3d02a4b..5c1202af0748 100644
@@ -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);
Signature · 1 line
2.18.0
#1 lore raw
Quoted 7 lines · Arnd Bergmann

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'

I'm a bit surprised by this - the code is not new, it just got moved out of the drivers, and I don't see any protections there against CONFIG_MMU ??

Quoted 4 lines

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.

Hrm. So this code doesn't work at all on NOMMU, it relies on remap_pfn_range, which always fails on those kernels,

Due to this of this the entirety of INFINIBAND_USER_ACCESS is broken.

I think a kconfig change is the better way to go?

Jason

author
#2 lore raw
Quoted 5 lines · Jason Gunthorpe
Quoted 3 lines · Arnd Bergmann

The zap_vma_ptes() is declared but not defined on NOMMU kernels, causing a link error for the newly added uverbs code:

Quoted 8 lines
Quoted 4 lines

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'

I'm a bit surprised by this - the code is not new, it just got moved out of the drivers, and I don't see any protections there against CONFIG_MMU ??

I think I just never hit those in my randconfig builds. Out of the three drivers, one is 64-bit only, and the others depend on PCI. The nommu configurations I'm testing in randconfig are all 32-bit without PCI.

Quoted 11 lines
Quoted 4 lines

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.

Hrm. So this code doesn't work at all on NOMMU, it relies on remap_pfn_range, which always fails on those kernels,

Due to this of this the entirety of INFINIBAND_USER_ACCESS is broken.

I think a kconfig change is the better way to go?

Works for me. Can you just commit that yourself with 'Reported-by:
Arnd Bergmann <[email protected]>' then?

Arnd