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? - 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"). - 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 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? - 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. - Why is TEE_SHM_REGISTER implemented at the TEE driver level when it is specific to OP-TEE? How to better abstract that away? 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! Tyler > > -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 > > >
