tee: convert get_user_pages() --> pin_user_pages()

This code was using get_user_pages*(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1]. That means that it's
time to convert the get_user_pages*() + put_page() calls to
pin_user_pages*() + unpin_user_pages() calls.

Factor out a new, small release_registered_pages() function, in
order to consolidate the logic for discerning between
TEE_SHM_USER_MAPPED and TEE_SHM_KERNEL_MAPPED pages. This also
absorbs the kfree() call that is also required there.

There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
    https://lwn.net/Articles/807108/

Cc: Jens Wiklander <jens.wiklander@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: tee-dev@lists.linaro.org
Cc: linux-media@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linaro-mm-sig@lists.linaro.org
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 827ac3d..00472f5 100644 (file)
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -12,6 +12,22 @@
 #include <linux/uio.h>
 #include "tee_private.h"
 
+static void release_registered_pages(struct tee_shm *shm)
+{
+       if (shm->pages) {
+               if (shm->flags & TEE_SHM_USER_MAPPED) {
+                       unpin_user_pages(shm->pages, shm->num_pages);
+               } else {
+                       size_t n;
+
+                       for (n = 0; n < shm->num_pages; n++)
+                               put_page(shm->pages[n]);
+               }
+
+               kfree(shm->pages);
+       }
+}
+
 static void tee_shm_release(struct tee_shm *shm)
 {
        struct tee_device *teedev = shm->ctx->teedev;
@@ -32,17 +48,13 @@ static void tee_shm_release(struct tee_shm *shm)
 
                poolm->ops->free(poolm, shm);
        } else if (shm->flags & TEE_SHM_REGISTER) {
-               size_t n;
                int rc = teedev->desc->ops->shm_unregister(shm->ctx, shm);
 
                if (rc)
                        dev_err(teedev->dev.parent,
                                "unregister shm %p failed: %d", shm, rc);
 
-               for (n = 0; n < shm->num_pages; n++)
-                       put_page(shm->pages[n]);
-
-               kfree(shm->pages);
+               release_registered_pages(shm);
        }
 
        teedev_ctx_put(shm->ctx);
@@ -228,7 +240,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
        }
 
        if (flags & TEE_SHM_USER_MAPPED) {
-               rc = get_user_pages_fast(start, num_pages, FOLL_WRITE,
+               rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE,
                                         shm->pages);
        } else {
                struct kvec *kiov;
@@ -292,18 +304,12 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, unsigned long addr,
        return shm;
 err:
        if (shm) {
-               size_t n;
-
                if (shm->id >= 0) {
                        mutex_lock(&teedev->mutex);
                        idr_remove(&teedev->idr, shm->id);
                        mutex_unlock(&teedev->mutex);
                }
-               if (shm->pages) {
-                       for (n = 0; n < shm->num_pages; n++)
-                               put_page(shm->pages[n]);
-                       kfree(shm->pages);
-               }
+               release_registered_pages(shm);
        }
        kfree(shm);
        teedev_ctx_put(ctx);