From:   Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     jgg@ziepe.ca, Liam.Howlett@Oracle.com, jhubbard@nvidia.com,
        david@redhat.com, willy@infradead.org, akpm@linux-foundation.org,
        linux-kernel-mentees@lists.linuxfoundation.org,
        Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Subject: [RFC PATCH v1 1/1] linux: mm_types: allow to modified the vm_flags in vm_area_struct
Date:   Sun, 12 Mar 2023 23:42:50 +0100
Message-Id: <20230312224250.425727-1-vincenzopalazzodev@gmail.com>
MIME-Version: 1.0
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Precedence: bulk

With 6.3-rc1 is not possible to build the following drivers

- nvidia, that the compilation returns the following errors

/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c: In function ‘nvidia_mmap_numa’:
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:455:19: error: assignment of read-only member ‘vm_flags’
  455 |     vma->vm_flags |= VM_MIXEDMAP;
      |                   ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c: In function ‘nvidia_mmap_helper’:
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:599:23: error: assignment of read-only member ‘vm_flags’
  599 |         vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND;
      |                       ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:666:23: error: assignment of read-only member ‘vm_flags’
  666 |         vma->vm_flags |= (VM_IO | VM_LOCKED | VM_RESERVED);
      |                       ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:667:23: error: assignment of read-only member ‘vm_flags’
  667 |         vma->vm_flags |= (VM_DONTEXPAND | VM_DONTDUMP);
      |                       ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:673:23: error: assignment of read-only member ‘vm_flags’
  673 |         vma->vm_flags &= ~VM_WRITE;
      |                       ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:674:23: error: assignment of read-only member ‘vm_flags’
  674 |         vma->vm_flags &= ~VM_MAYWRITE;
      |                       ^~
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c: In function ‘nv_encode_caching’:
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:353:16: warning: this statement may fall through [-Wimplicit-fallthrough=]
  353 |             if (NV_ALLOW_CACHING(memory_type))
      |                ^
/var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.c:356:9: note: here
  356 |         default:
      |         ^~~~~~~
make[2]: *** [scripts/Makefile.build:252: /var/lib/dkms/nvidia/525.89.02/build/nvidia/nv-mmap.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [Makefile:2028: /var/lib/dkms/nvidia/525.89.02/build] Error 2
make[1]: Leaving directory '/home/vincenzopalazzo/gittea/linux'
make: *** [Makefile:82: modules] Error 2
------

- vboxhost/7.0.6_OSE where the build fails with the following errors
DKMS make.log for vboxhost-7.0.6_OSE for kernel 6.3.0-rc1-00231-g511e7733223b (x86_64)
Sat Mar 11 04:21:34 PM UTC 2023
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/linux/VBoxNetFlt-linux.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetadp/linux/VBoxNetAdp-linux.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/VBoxNetFlt.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/linux/SUPDrv-linux.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrv.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetadp/VBoxNetAdp.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrvGip.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/SUPR0IdcClient.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrvSem.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/SUPR0IdcClientComponent.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/linux/SUPR0IdcClient-linux.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPDrvTracer.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/SUPLibAll.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/common/string/strformatrt.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-agnostic1.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-agnostic2.o
  CC [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-os-specific.o
  LD [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetadp/vboxnetadp.o
In file included from /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-os-specific.c:43:
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c: In function ‘rtR0MemObjNativeLockUser’:
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c:1404:39: error: assignment of read-only member ‘vm_flags’
 1404 |                 papVMAs[rc]->vm_flags |= VM_DONTCOPY | VM_LOCKED;
      |                                       ^~
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c: In function ‘rtR0MemObjNativeMapUser’:
/var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/r0drv/linux/memobj-r0drv-linux.c:1876:35: error: assignment of read-only member ‘vm_flags’
 1876 |                     vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
      |                                   ^~
make[2]: *** [scripts/Makefile.build:252: /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv/combined-os-specific.o] Error 1
make[2]: *** Waiting for unfinished jobs....
  LD [M]  /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxnetflt/vboxnetflt.o
make[1]: *** [scripts/Makefile.build:494: /var/lib/dkms/vboxhost/7.0.6_OSE/build/vboxdrv] Error 2
make: *** [Makefile:2028: /var/lib/dkms/vboxhost/7.0.6_OSE/build] Error 2
-----

The commands that I use to build these drivers are:

- sudo dkms install --no-depmod nvidia/525.89.02 -k 6.3.0-rc1-00231-g511e7733223b
- sudo dkms install --no-depmod vboxhost/7.0.6_OSE -k 6.3.0-rc1-00231-g511e7733223b

The following commit reverts the const constraint that was added in [1],
and also I tested this patch on my system and all started again as
6.2.2.

[1] https://lore.kernel.org/all/20230126193752.297968-3-surenb@google.com/T/#u

Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
---
 include/linux/mm_types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 0722859c3647..a354eb60c7e8 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -497,7 +497,7 @@ struct vm_area_struct {
 	 * To modify use vm_flags_{init|reset|set|clear|mod} functions.
 	 */
 	union {
-		const vm_flags_t vm_flags;
+		vm_flags_t vm_flags;
 		vm_flags_t __private __vm_flags;
 	};
 
-- 
2.39.2