[PATCH v3] tee: convert convert get_user_pages() --> pin_user_pages()

From: John Hubbard
Date: Mon Aug 24 2020 - 17:11:30 EST


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@xxxxxxxxxx>
Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
Cc: tee-dev@xxxxxxxxxxxxxxxx
Cc: linux-media@xxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx
Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---

OK, one more try, this time actually handling the _USER_MAPPED vs.
_KERNEL_MAPPED pages!

thanks,
John Hubbard
NVIDIA

drivers/tee/tee_shm.c | 32 +++++++++++++++++++-------------
1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 827ac3d0fea9..00472f5ce22e 100644
--- 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);
--
2.28.0