+ Rijo
On Wed, 9 Jun 2021 at 11:16, Tyler Hicks tyhicks@linux.microsoft.com wrote:
On 2021-06-09 09:59:04, Sumit Garg wrote:
Hi Tyler,
Hey Sumit - Thanks for the review.
On Wed, 9 Jun 2021 at 05:55, Tyler Hicks tyhicks@linux.microsoft.com wrote:
Uncouple the registration of dynamic shared memory buffers from the TEE_SHM_DMA_BUF flag. Drivers may wish to allocate dynamic shared memory regions but do not need them to be backed by a dma-buf when the memory region is private to the driver.
In this case drivers should use tee_shm_register() instead where the memory allocated is actually private to the driver. However, you need to remove TEE_SHM_DMA_BUF as a mandatory flag for tee_shm_register(). Have a look at an example here [1]. So modifying tee_shm_alloc() for this purpose doesn't look appropriate to me.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/secu...
I noticed what you did in commit 2a6ba3f794e8 ("tee: enable support to register kernel memory") and considered moving ftpm and tee_bnxt_fw over to tee_shm_register(). I think that's likely the right long term approach but I decided against it since this series is a minimal set of bug fixes that will hopefully go to stable (I'm affected by these bugs in 5.4). Here are my reasons for feeling like moving to tee_shm_register() isn't minimal in terms of a stable-focused fix:
- tee_shm_alloc() looks like it should work fine with AMD-TEE today. tee_shm_register() definitely does not since AMD-TEE doesn't provide a .shm_register or .shm_unregister hook. This may break existing users of AMD-TEE?
AFAIK, ftpm and tee_bnxt_fw drivers only support OP-TEE at this point. See ftpm_tee_match() and optee_ctx_match() APIs in corresponding drivers.
- tee_shm_register() has not historically been used for kernel allocations and is not fixed wrt the bug that Jens fixed in commit f1bbacedb0af ("tee: don't assign shm id for private shms").
Yes, that's what I meant earlier to make the TEE_SHM_DMA_BUF flag optional.
- tee_shm_alloc() performs allocations using contiguous pages from alloc_pages() while tee_shm_register() performs non-contiguous allocations with kcalloc(). I suspect this would be fine but I don't know the secure world side of these things well enough to assess the risk involved with such a change on the kernel side.
I don't think that would make any difference.
I should have mentioned this in the cover letter but my hope was that these minimal changes would be accepted and then additional work could be done to merge tee_shm_alloc() and tee_shm_register() in a way that would allow the caller to request contiguous or non-contiguous pages, fix up the additional issues mentioned above, and then adjust the call sites in ftpm and tee_bnxt_fw as appropriate.
I think that's a bigger set of changes because there are several things that still confuse/concern me:
- Why does tee_shm_alloc() use TEE_SHM_MAPPED while tee_shm_register() uses TEE_SHM_KERNEL_MAPPED or TEE_SHM_USER_MAPPED? Why do all three exist?
AFAIK, its due the the inherent nature of tee_shm_alloc() and tee_shm_register() where tee_shm_alloc() doesn't need to know whether its a kernel or user-space memory since it is the one that allocates whereas tee_shm_register() need to know that since it has to register pre-allocated client memory.
- Why does tee_shm_register() unconditionally use non-contiguous allocations without ever taking into account whether or not OPTEE_SMC_SEC_CAP_DYNAMIC_SHM was set? It sounds like that's required from my reading of https://optee.readthedocs.io/en/latest/architecture/core.html#noncontiguous-....
Yeah, but do we have platforms in OP-TEE that don't support dynamic shared memory? I guess it has become the sane default which is a mandatory requirement when it comes to OP-TEE driver in u-boot.
- Why is TEE_SHM_REGISTER implemented at the TEE driver level when it is specific to OP-TEE? How to better abstract that away?
I would like you to go through Section "3.2.4. Shared Memory" in TEE Client API Specification. There are two standard ways for shared memory approach with TEE:
1. A Shared Memory block can either be existing Client Application memory (kernel driver in our case) which is subsequently registered with the TEE Client API (using tee_shm_register() in our case).
2. Or memory which is allocated on behalf of the Client Application using the TEE Client API (using tee_shm_alloc() in our case).
Let me know if you agree with the more minimal approach that I took for these bug fix series or still feel like tee_shm_register() should be fixed up so that it is usable. Thanks!
From drivers perspective I think the change should be:
tee_shm_alloc()
to
kcalloc() tee_shm_register()
-Sumit
Allow callers of tee_shm_alloc() to specify the TEE_SHM_REGISTER flag to. request registration. If the TEE implementation does not require dynamic shared memory to be registered, clear the flag prior to calling the corresponding pool alloc function. Update the OP-TEE driver to respect TEE_SHM_REGISTER, rather than TEE_SHM_DMA_BUF, when deciding whether to (un)register on alloc/free operations. The AMD-TEE driver continues to ignore the TEE_SHM_REGISTER flag.
Signed-off-by: Tyler Hicks tyhicks@linux.microsoft.com
drivers/tee/optee/shm_pool.c | 5 ++--- drivers/tee/tee_shm.c | 11 ++++++++++- 2 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/drivers/tee/optee/shm_pool.c b/drivers/tee/optee/shm_pool.c index da06ce9b9313..6054343a29fb 100644 --- a/drivers/tee/optee/shm_pool.c +++ b/drivers/tee/optee/shm_pool.c @@ -27,7 +27,7 @@ static int pool_op_alloc(struct tee_shm_pool_mgr *poolm, shm->paddr = page_to_phys(page); shm->size = PAGE_SIZE << order;
if (shm->flags & TEE_SHM_DMA_BUF) {
if (shm->flags & TEE_SHM_REGISTER) { unsigned int nr_pages = 1 << order, i; struct page **pages;@@ -42,7 +42,6 @@ static int pool_op_alloc(struct tee_shm_pool_mgr *poolm, page++; }
shm->flags |= TEE_SHM_REGISTER; rc = optee_shm_register(shm->ctx, shm, pages, nr_pages, (unsigned long)shm->kaddr); kfree(pages);@@ -60,7 +59,7 @@ static int pool_op_alloc(struct tee_shm_pool_mgr *poolm, static void pool_op_free(struct tee_shm_pool_mgr *poolm, struct tee_shm *shm) {
if (shm->flags & TEE_SHM_DMA_BUF)
if (shm->flags & TEE_SHM_REGISTER) optee_shm_unregister(shm->ctx, shm); free_pages((unsigned long)shm->kaddr, get_order(shm->size));diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c index 00472f5ce22e..1c0176550b9c 100644 --- a/drivers/tee/tee_shm.c +++ b/drivers/tee/tee_shm.c @@ -117,7 +117,7 @@ struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags) return ERR_PTR(-EINVAL); }
if ((flags & ~(TEE_SHM_MAPPED | TEE_SHM_DMA_BUF))) {
if ((flags & ~(TEE_SHM_MAPPED | TEE_SHM_DMA_BUF | TEE_SHM_REGISTER))) { dev_err(teedev->dev.parent, "invalid shm flags 0x%x", flags); return ERR_PTR(-EINVAL); }@@ -137,6 +137,15 @@ struct tee_shm *tee_shm_alloc(struct tee_context *ctx, size_t size, u32 flags) goto err_dev_put; }
if (!teedev->desc->ops->shm_register ||!teedev->desc->ops->shm_unregister) {/* registration is not required by the TEE implementation */flags &= ~TEE_SHM_REGISTER;} else if (flags & TEE_SHM_DMA_BUF) {/* all dma-buf backed shm allocations are registered */flags |= TEE_SHM_REGISTER;}shm->flags = flags | TEE_SHM_POOL; shm->ctx = ctx; if (flags & TEE_SHM_DMA_BUF)-- 2.25.1