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Date: Wed, 29 Nov 2023 10:09:35 +0100
From: Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>
To: Sumit Garg <sumit.garg@...aro.org>
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 v3] tee: Use iov_iter to better support shared buffer
registration
Hi Sumit,
On 11/29/23 07:57, Sumit Garg wrote:
> Hi Arnaud,
>
> On Tue, 28 Nov 2023 at 13:49, Arnaud Pouliquen
> <arnaud.pouliquen@...s.st.com> wrote:
>>
>> It is not possible to register buffers allocated with vmalloc.
>
> I would rephrase it as:
>
> 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 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 | 77 ++++++++++++++++++++++++-------------------
>> 1 file changed, 43 insertions(+), 34 deletions(-)
>>
>> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
>> index 673cf0359494..fe0a205be7ef 100644
>> --- a/drivers/tee/tee_shm.c
>> +++ b/drivers/tee/tee_shm.c
>> @@ -22,23 +22,16 @@ 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;
>> + /*
>> + * iov_iter_extract_kvec_pages does not get reference on the pages,
>> + * get a pin on them.
>> + */
>> + 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 +207,13 @@ 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, length, len, off;
>> void *ret;
>> int rc;
>>
>> @@ -245,31 +238,32 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
>> shm->flags = flags;
>> shm->ctx = ctx;
>> shm->id = id;
>> - addr = untagged_addr(addr);
>> + addr = (unsigned long)iter_iov_addr(iter);
>
> Why did you drop untagged_addr() here?
Right, better too keep it
>
>> + length = iter_iov_len(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);
>> + len = iov_iter_extract_pages(iter, &shm->pages, LONG_MAX, num_pages, 0,
>> + &off);
>> + if (len != length) {
>
> Any particular reason for this check?
Cross-checking to answer to your comment, I just released that
iov_iter_extract_pages returns ssize_t not size_t.
Therefore, I need to change the type of len and replace the check with
(len <= 0).
>
>> + ret = len ? ERR_PTR(len) : ERR_PTR(-ENOMEM);
>> goto err_put_shm_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) {
>> @@ -307,6 +301,8 @@ 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 iovec iov;
>> + struct iov_iter iter;
>> void *ret;
>> int id;
>>
>> @@ -319,7 +315,10 @@ 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);
>> + iov.iov_base = (void __user *)addr;
>> + iov.iov_len = length;
>> + iov_iter_init(&iter, ITER_DEST, &iov, 1, length);
>
> We should rather use import_ubuf() instead of this and the above
> access_ok() check.
Thanks for the advice, I will test it.
>
>> + shm = register_shm_helper(ctx, &iter, flags, id);
>> if (IS_ERR(shm)) {
>> mutex_lock(&teedev->mutex);
>> idr_remove(&teedev->idr, id);
>> @@ -351,9 +350,19 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
>> struct tee_shm *tee_shm_register_kernel_buf(struct tee_context *ctx,
>> void *addr, size_t length)
>> {
>> + struct tee_shm *shm;
>> u32 flags = TEE_SHM_DYNAMIC;
>> + struct kvec kvec;
>> + struct iov_iter iter;
>>
>> - return register_shm_helper(ctx, (unsigned long)addr, length, flags, -1);
>> + kvec.iov_base = addr;
>> + kvec.iov_len = length;
>> + iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, length);
>> + shm = register_shm_helper(ctx, &iter, flags, -1);
>> + if (!IS_ERR(shm))
>> + shm_get_kernel_pages(shm->pages, shm->num_pages);
>
> The kernel pages reference should be taken before invoking
> teedev->desc->ops->shm_register(). So you should move this to
> register_shm_helper() instead. You can use iov_iter_is_kvec() to know
> if you have to get a reference or not.
Yes much better
Thanks!
Arnaud
>
> -Sumit
>
>> +
>> + return shm;
>> }
>> EXPORT_SYMBOL_GPL(tee_shm_register_kernel_buf);
>>
>> --
>> 2.25.1
>>
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