tee: Remove vmalloc page support

The kernel pages used by shm_get_kernel_pages() are allocated using
GFP_KERNEL through the following call stack:

trusted_instantiate()
	trusted_payload_alloc() -> GFP_KERNEL
	<trusted key op>
		tee_shm_register_kernel_buf()
			register_shm_helper()
				shm_get_kernel_pages()

Where <trusted key op> is one of:

	trusted_key_unseal()
	trusted_key_get_random()
	trusted_key_seal()

Remove the vmalloc page support from shm_get_kernel_pages().  Replace
with a warn on once.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/tee_shm.c

@@ -24,23 +24,12 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count)
 static int shm_get_kernel_pages(unsigned long start, size_t page_count,
 				struct page **pages)
 {
+	struct kvec *kiov;
 	size_t n;
 	int rc;
 
-	if (is_vmalloc_addr((void *)start)) {
-		struct page *page;
-
-		for (n = 0; n < page_count; n++) {
-			page = vmalloc_to_page((void *)(start + PAGE_SIZE * n));
-			if (!page)
-				return -ENOMEM;
-
-			get_page(page);
-			pages[n] = page;
-		}
-		rc = page_count;
-	} else {
-		struct kvec *kiov;
+	if (WARN_ON_ONCE(is_vmalloc_addr((void *)start)))
+		return -EINVAL;
 
 	kiov = kcalloc(page_count, sizeof(*kiov), GFP_KERNEL);
 	if (!kiov)
@@ -53,7 +42,6 @@ static int shm_get_kernel_pages(unsigned long start, size_t page_count,
 
 	rc = get_kernel_pages(kiov, page_count, 0, pages);
 	kfree(kiov);
-	}
 
 	return rc;
 }