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Date: Thu, 30 Nov 2023 17:30:17 +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 Thu, 30 Nov 2023 at 14:38, Arnaud POULIQUEN
<arnaud.pouliquen@...s.st.com> wrote:
>
>
>
> On 11/30/23 08:54, Sumit Garg wrote:
> > 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.
> > */
> >
>
> I spent some time debugging this part. Since we use the same API for both user
> and kernel buffers, we wouldn't expect to have any specific actions to take.
> Therefore, I thought it would be helpful to add a comment explaining the reason
> for this specific code, rather than go deeper into iov_iter to understand it.
>
Fair enough, let's keep it with s/pin/reference/.
> But if you don't see the value, I can remove the comment.
>
> >> + */
> >> + 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.
>
> My apologies, I re-added import_ubuf() during testing to debug an issue and
I suppose you intended to mention access_ok() here, BTW, no worries :).
-Sumit
> forgot to
> remove it afterwards.
>
> Thanks and regards,
> Arnaud
>
> >
> > -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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