linux-kernel - [PATCH v3] tee: convert convert get_user_pages() --> pin_user

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Message-ID: <20200824211125.1867329-1-jhubbard@nvidia.com>
Date:   Mon, 24 Aug 2020 14:11:25 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     <jens.wiklander@...aro.org>
CC:     <arm@...nel.org>, <jhubbard@...dia.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <olof@...om.net>, <soc@...nel.org>,
        <tee-dev@...ts.linaro.org>, Sumit Semwal <sumit.semwal@...aro.org>,
        <linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>
Subject: [PATCH v3] tee: convert 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@...aro.org>
Cc: Sumit Semwal <sumit.semwal@...aro.org>
Cc: tee-dev@...ts.linaro.org
Cc: linux-media@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org
Cc: linaro-mm-sig@...ts.linaro.org
Signed-off-by: John Hubbard <jhubbard@...dia.com>
---

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