+ Rijo On Wed, 9 Jun 2021 at 11:16, Tyler Hicks <tyhicks@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> 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/security/keys/trusted-keys/trusted_tee.c#n73 > > 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-shared-buffers. 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@xxxxxxxxxxxxxxxxxxx> > > > --- > > > 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 > > > > >
