Re: [PATCH] tee: add FOLL_LONGTERM for CMA case when alloc shm

On Wed, 17 May 2023 at 13:04, Christoph Hellwig [off-list ref] wrote:

quoted

+     u32 page_flag = FOLL_WRITE;

      if (!tee_device_get(teedev))
              return ERR_PTR(-EINVAL);

@@ -255,9 +256,11 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
              ret = ERR_PTR(-ENOMEM);
              goto err_free_shm;
      }
-
+#if IS_ENABLED(CONFIG_CMA)
+     page_flag |= FOLL_LONGTERM;
+#endif
      if (flags & TEE_SHM_USER_MAPPED)

If this mapping is long live it should always use FOLL_LONGTERM.

It depends on the userspace application needs. However, I think it
should be safe to use FOLL_LONGTERM by default to serve cases like
secure media playback.

The ifdef does not make sense.

Agree.

-Sumit

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