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Date: Thu, 30 Nov 2023 13:24:49 +0530
From: Sumit Garg <sumit.garg@...aro.org>
To: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
Cc: Jens Wiklander <jens.wiklander@...aro.org>,
Christoph Hellwig <hch@...radead.org>,
op-tee@...ts.trustedfirmware.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] tee: Use iov_iter to better support shared buffer registration
On Wed, 29 Nov 2023 at 22:15, Arnaud Pouliquen
<arnaud.pouliquen@...s.st.com> wrote:
>
> Currently it's not possible to register kernel buffers with TEE
> which are allocated via vmalloc.
>
> Use iov_iter and associated helper functions to manage the page
> registration for all type of memories.
>
> Suggested-by: Christoph Hellwig <hch@...radead.org>
> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@...s.st.com>
> ---
> Update from V3 to V4:
> - improve commit message,
> - use import_ubuf() instead of iov_iter_init(),
> - move shm_get_kernel_pages in register_shm_helper,
> - put back untagged_addr in register_shm_helper(),
> - move the comment related to pin pages from shm_get_kernel_pages()
> to register_shm_helper().
>
> Update from V2 to V3:
> - break lines longer than 80 columns.
>
> Update from V1 to V2:
> - replace ITER_SOURCE by ITER_DEST flag in tee_shm_register_user_buf(),
> - replace IS_ERR_OR NULL(shm) by IS_ERR(shm) in tee_shm_register_user_buf().
>
> V1:
> The support of buffer registration allocated with vmalloc is no more
> available since c83900393aa1 ("tee: Remove vmalloc page support").
>
> This patch is an alternative to a revert and resulted from a discussion
> with Christopher Hellwig [1].
>
> This patch has been tested using xtest tool in optee qemu environment [2]
> and using the series related to the remoteproc tee that should be
> proposed soon [3].
>
> References:
> [1] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb2@foss.st.com/T/#m8ec683c44fcd9b69c2aee42eaed0793afac9dd18in
> [2] https://optee.readthedocs.io/en/latest/building/devices/qemu.html#build-instructions
> [3] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb2@foss.st.com/T/#maca0a1fc897aadd54c7deac432e11473fe970d1d
> ---
> drivers/tee/tee_shm.c | 83 ++++++++++++++++++++++++-------------------
> 1 file changed, 46 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
> index 673cf0359494..ac73e8143233 100644
> --- a/drivers/tee/tee_shm.c
> +++ b/drivers/tee/tee_shm.c
> @@ -22,23 +22,12 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count)
> put_page(pages[n]);
> }
>
> -static int shm_get_kernel_pages(unsigned long start, size_t page_count,
> - struct page **pages)
> +static void shm_get_kernel_pages(struct page **pages, size_t page_count)
> {
> - struct page *page;
> size_t n;
>
> - if (WARN_ON_ONCE(is_vmalloc_addr((void *)start) ||
> - is_kmap_addr((void *)start)))
> - return -EINVAL;
> -
> - page = virt_to_page((void *)start);
> - for (n = 0; n < page_count; n++) {
> - pages[n] = page + n;
> + for (n = 0; n < page_count; n++)
> get_page(pages[n]);
> - }
> -
> - return page_count;
> }
>
> static void release_registered_pages(struct tee_shm *shm)
> @@ -214,13 +203,14 @@ struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size)
> EXPORT_SYMBOL_GPL(tee_shm_alloc_priv_buf);
>
> static struct tee_shm *
> -register_shm_helper(struct tee_context *ctx, unsigned long addr,
> - size_t length, u32 flags, int id)
> +register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,
> + int id)
> {
> struct tee_device *teedev = ctx->teedev;
> struct tee_shm *shm;
> - unsigned long start;
> - size_t num_pages;
> + unsigned long start, addr;
> + size_t num_pages, off;
> + ssize_t len;
> void *ret;
> int rc;
>
> @@ -245,31 +235,38 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
> shm->flags = flags;
> shm->ctx = ctx;
> shm->id = id;
> - addr = untagged_addr(addr);
> + addr = untagged_addr((unsigned long)iter_iov_addr(iter));
> start = rounddown(addr, PAGE_SIZE);
> - shm->offset = addr - start;
> - shm->size = length;
> - num_pages = (roundup(addr + length, PAGE_SIZE) - start) / PAGE_SIZE;
> + num_pages = iov_iter_npages(iter, INT_MAX);
> + if (!num_pages) {
> + ret = ERR_PTR(-ENOMEM);
> + goto err_ctx_put;
> + }
> +
> shm->pages = kcalloc(num_pages, sizeof(*shm->pages), GFP_KERNEL);
> if (!shm->pages) {
> ret = ERR_PTR(-ENOMEM);
> goto err_free_shm;
> }
>
> - if (flags & TEE_SHM_USER_MAPPED)
> - rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE,
> - shm->pages);
> - else
> - rc = shm_get_kernel_pages(start, num_pages, shm->pages);
> - if (rc > 0)
> - shm->num_pages = rc;
> - if (rc != num_pages) {
> - if (rc >= 0)
> - rc = -ENOMEM;
> - ret = ERR_PTR(rc);
> - goto err_put_shm_pages;
> + len = iov_iter_extract_pages(iter, &shm->pages, LONG_MAX, num_pages, 0,
> + &off);
> + if (unlikely(len <= 0)) {
> + ret = len ? ERR_PTR(len) : ERR_PTR(-ENOMEM);
> + goto err_free_shm_pages;
> }
>
> + /*
> + * iov_iter_extract_kvec_pages does not get reference on the pages,
> + * get a pin on them.
I think you meant: "get a reference on them". But I don't see the
value of this comment since iov_iter_extract_kvec_pages() already has
been commented properly as follows:
/*
* Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
* This does not get references on the pages, nor does it get a pin on them.
*/
> + */
> + if (iov_iter_is_kvec(iter))
> + shm_get_kernel_pages(shm->pages, num_pages);
> +
> + shm->offset = off;
> + shm->size = len;
> + shm->num_pages = num_pages;
> +
> rc = teedev->desc->ops->shm_register(ctx, shm, shm->pages,
> shm->num_pages, start);
> if (rc) {
> @@ -279,10 +276,11 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
>
> return shm;
> err_put_shm_pages:
> - if (flags & TEE_SHM_USER_MAPPED)
> + if (!iov_iter_is_kvec(iter))
> unpin_user_pages(shm->pages, shm->num_pages);
> else
> shm_put_kernel_pages(shm->pages, shm->num_pages);
> +err_free_shm_pages:
> kfree(shm->pages);
> err_free_shm:
> kfree(shm);
> @@ -307,8 +305,9 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
> u32 flags = TEE_SHM_USER_MAPPED | TEE_SHM_DYNAMIC;
> struct tee_device *teedev = ctx->teedev;
> struct tee_shm *shm;
> + struct iov_iter iter;
> void *ret;
> - int id;
> + int id, err;
>
> if (!access_ok((void __user *)addr, length))
> return ERR_PTR(-EFAULT);
> @@ -319,7 +318,11 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
> if (id < 0)
> return ERR_PTR(id);
>
> - shm = register_shm_helper(ctx, addr, length, flags, id);
> + err = import_ubuf(ITER_DEST, (void __user *)addr, length, &iter);
As I mentioned in a previous review, import_ubuf() already does the
access_ok() check, so we don't need the extra access_ok() check above.
Also, you should move import_ubuf() to be the first invocation within
this API.
-Sumit
> + if (err)
> + return ERR_PTR(err);
> +
> + shm = register_shm_helper(ctx, &iter, flags, id);
> if (IS_ERR(shm)) {
> mutex_lock(&teedev->mutex);
> idr_remove(&teedev->idr, id);
> @@ -352,8 +355,14 @@ struct tee_shm *tee_shm_register_kernel_buf(struct tee_context *ctx,
> void *addr, size_t length)
> {
> u32 flags = TEE_SHM_DYNAMIC;
> + struct kvec kvec;
> + struct iov_iter iter;
> +
> + kvec.iov_base = addr;
> + kvec.iov_len = length;
> + iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, length);
>
> - return register_shm_helper(ctx, (unsigned long)addr, length, flags, -1);
> + return register_shm_helper(ctx, &iter, flags, -1);
> }
> EXPORT_SYMBOL_GPL(tee_shm_register_kernel_buf);
>
> --
> 2.25.1
>
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