From: Tyler Hicks <tyhicks@linux.microsoft.com>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: "Jens Wiklander" <jens.wiklander@linaro.org>,
"Allen Pais" <apais@linux.microsoft.com>,
"Peter Huewe" <peterhuewe@gmx.de>,
"Jarkko Sakkinen" <jarkko@kernel.org>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Vikas Gupta" <vikas.gupta@broadcom.com>,
"Thirupathaiah Annapureddy" <thiruan@microsoft.com>,
"Pavel Tatashin" <pasha.tatashin@soleen.com>,
"Rafał Miłecki" <zajec5@gmail.com>,
op-tee@lists.trustedfirmware.org,
linux-integrity <linux-integrity@vger.kernel.org>,
bcm-kernel-feedback-list@broadcom.com,
linux-mips@vger.kernel.org,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 5/7] tee: Support shm registration without dma-buf backing
Date: Wed, 9 Jun 2021 00:46:21 -0500 [thread overview]
Message-ID: <20210609054621.GB4910@sequoia> (raw)
In-Reply-To: <CAFA6WYOZC0iHzZm6pOxz31eW_=8g2wyJdm4wiOGKggO6-a9MdA@mail.gmail.com>
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/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@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
> >
>
next prev parent reply other threads:[~2021-06-09 5:46 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 0:23 [PATCH v3 0/7] tee: Improve support for kexec and kdump Tyler Hicks
2021-06-09 0:23 ` [PATCH v3 1/7] optee: Fix memory leak when failing to register shm pages Tyler Hicks
2021-06-09 0:23 ` [PATCH v3 2/7] optee: Refuse to load the driver under the kdump kernel Tyler Hicks
2021-06-09 0:23 ` [PATCH v3 3/7] optee: fix tee out of memory failure seen during kexec reboot Tyler Hicks
2021-06-09 0:23 ` [PATCH v3 4/7] optee: Clear stale cache entries during initialization Tyler Hicks
2021-06-09 0:23 ` [PATCH v3 5/7] tee: Support shm registration without dma-buf backing Tyler Hicks
2021-06-09 4:29 ` Sumit Garg
2021-06-09 5:46 ` Tyler Hicks [this message]
2021-06-09 10:52 ` Sumit Garg
2021-06-09 12:15 ` Jens Wiklander
2021-06-09 13:42 ` Tyler Hicks
2021-06-09 13:51 ` Tyler Hicks
2021-06-10 7:34 ` Jens Wiklander
2021-06-10 21:00 ` Tyler Hicks
2021-06-10 7:49 ` Jens Wiklander
2021-06-10 21:05 ` Tyler Hicks
2021-06-10 7:40 ` Allen Pais
2021-06-10 7:18 ` Jens Wiklander
2021-06-10 12:14 ` Sumit Garg
2021-06-09 0:23 ` [PATCH v3 6/7] tpm_ftpm_tee: Free and unregister dynamic shared memory during kexec Tyler Hicks
2021-06-09 0:23 ` [PATCH v3 7/7] firmware: tee_bnxt: Release shm, session, and context " Tyler Hicks
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