Re: [PATCH] tee: convert convert get_user_pages() --> pin_user_pages()

[John Hubbard]

On 2020-05-18 22:18, John Hubbard wrote:

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.



Looks like I accidentally doubled a word on the subject line:
"convert convert". :)

I'd appreciate it a maintainer could remove one of those for
me, while applying the patch, assuming that we don't need a
v2 for other reasons.


thanks,
--
John Hubbard
NVIDIA

[PATCH] tee: convert convert get_user_pages() --> pin_user_pages()

[John Hubbard]

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.

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 
Cc: Sumit Semwal 
Cc: tee-...@lists.linaro.org
Cc: linux-me...@vger.kernel.org
Cc: dri-de...@lists.freedesktop.org
Cc: linaro-mm-...@lists.linaro.org
Signed-off-by: John Hubbard 
---

Note that I have only compile-tested this patch, although that does
also include cross-compiling for a few other arches.

thanks,
John Hubbard
NVIDIA

 drivers/tee/tee_shm.c | 12 +++-
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index bd679b72bd05..7dffc42d8d5a 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -31,16 +31,13 @@ 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]);
-
+   unpin_user_pages(shm->pages, shm->num_pages);
kfree(shm->pages);
}
 
@@ -226,7 +223,7 @@ struct tee_shm *tee_shm_register(struct tee_context *ctx, 
unsigned long addr,
goto err;
}
 
-   rc = get_user_pages_fast(start, num_pages, FOLL_WRITE, shm->pages);
+   rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE, shm->pages);
if (rc > 0)
shm->num_pages = rc;
if (rc != num_pages) {
@@ -271,16 +268,13 @@ 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(>mutex);
idr_remove(>idr, shm->id);
mutex_unlock(>mutex);
}
if (shm->pages) {
-   for (n = 0; n < shm->num_pages; n++)
-   put_page(shm->pages[n]);
+   unpin_user_pages(shm->pages, shm->num_pages);
kfree(shm->pages);
}
}
-- 
2.26.2