Re: [PATCH v2] drivers/crypto: Mark QCE as BROKEN

Demi Marie Obenour <[email protected]> Tue, 21 Jul 2026 14:29:39 -0400
Newsgroups	org.kernel.vger.linux-crypto,org.infradead.lists.linux-arm-kernel,org.kernel.vger.linux-arm-msm,org.kernel.vger.linux-kernel,org.kernel.vger.stable
Message-ID	<[email protected]>
On 7/21/26 04:24, Bartosz Golaszewski wrote:
> On Fri, Jul 17, 2026 at 06:18:48PM +1000, Herbert Xu wrote:
>> On Sun, Jul 12, 2026 at 05:31:31PM -0400, Demi Marie Obenour via B4 Relay wrote:
>>> From: Demi Marie Obenour <[email protected]>
>>>
>>> This driver is harmful:
>>>
>>> - It is much slower than the CPU [1] [2].
>>> - It Has a history of bugs [2] [3].
>>> - It does not have exclusive access to the hardware [4], causing races
>>>   with the secure world.
>>> - It register its implementations with too low a cra_priority for them
>>>   to be actually used [5].
>>>
>>> Therefore, disable it to ensure that nobody builds it into kernels they
>>> intend to ship.
>>>
>>> In the future, the driver will be used for processing restricted media
>>> content.  However, the kernel does not currently support this.  Since
>>> the driver will have future uses, allow building it if COMPILE_TEST is
>>> enabled.
>>>
>>> [1]: https://lore.kernel.org/r/[email protected]/
>>> [2]: https://lore.kernel.org/r/20250615031807.GA81869@sol/
>>> [3]: https://lore.kernel.org/r/[email protected]/
>>> [4]: https://lore.kernel.org/r/[email protected]/
>>> [5]: https://lore.kernel.org/r/20260524204537.GB110177@quark/
>>>
>>> Fixes: ec8f5d8f6f76 ("crypto: qce - Qualcomm crypto engine driver")
>>> Signed-off-by: Demi Marie Obenour <[email protected]>
>>> ---
>>> Changes in v2:
>>> - Add Fixes: ec8f5d8f6f76 ("crypto: qce - Qualcomm crypto engine driver")
>>> - Add Cc: [email protected]
>>> - Link to v1: https://lore.kernel.org/r/[email protected]
>>> ---
>>>  arch/arm/configs/multi_v7_defconfig | 1 -
>>>  arch/arm64/configs/defconfig        | 1 -
>>>  drivers/crypto/Kconfig              | 6 +++++-
>>>  3 files changed, 5 insertions(+), 3 deletions(-)
>>
>> Patch applied.  Thanks.
> 
> Hi Herbert,
> 
> I'd like to ask you to back this patch out. Admittedly I should have NAKed this
> under the v1 thread but I thought the discussion we had under the Shikra series
> and the subsequent patch making myself the maintainer of this driver (note: Demi
> did not Cc me on this nor the Qcom mailing list at linux-arm-msm) as well as the
> pending series[1] fixing the QCE issues was enough to imply we should not mark
> it as broken. Please consider applying [1] if the fixes in v6 are correct.
> 
> Bartosz
> 
> [1] https://lore.kernel.org/all/[email protected]/

Is the BAM locking patchset also needed?  My understanding is that
without it, the QCE driver can still produce wrong results due to races
with the TrustZone firmware.  Until it is merged and the self-tests
are fixed, the driver definitely needs to be marked BROKEN.

Also, what can the current driver do that cannot be done better using
software crypto?  I understand that you have future plans to add more
features to the driver, but those are not relevant to this discussion.

Finally, I very much appreciate the work you have done.  I don't
expect that the QCE driver will stay BROKEN forever.  This patch is
purely a reflection of the current state of the driver, the speed of
CPU-accelerated crypto, and the small message sizes used by the kernel.

That said, is drivers/crypto really the right place for a restricted
content driver?  A driver that uses dmabufs might be a better
alternative, and would be easier to integrate with the Direct Rendering
Manager (DRM) and Video for Linux 2 (V4L2) subsystems.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)
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