Re: [PATCH] crypto: qce - Remove driver

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Jul 23, 2026 at 10:06:45PM -0700, Eric Biggers wrote:
> This obsolete driver was already marked as BROKEN.  However, keeping
> BROKEN code around in the tree is unnecessary and causes problems.  It's
> much better to just remove it entirely.  Let's do that.
> 
> Crypto acceleration remains well-supported on Qualcomm SoCs via the
> Qualcomm Inline Crypto Engine and the ARMv8 Crypto Extensions, which are
> what Linux actually uses in practice.  The obsolete QCE driver is a
> dead-end approach.  It's extremely slow and just doesn't work well.
> 
> While there's been discussion around using QCE for restricted media
> content protection, that functionality has very little to do with the
> current crypto API driver and belongs in a separate, clean proposal
> (likely under a different subsystem/directory).
> 
> The extensive reasons for marking this driver as BROKEN were already
> documented in commit df373d39c6f0 ("crypto: qce - Mark QCE as BROKEN").
> 
> Since then, it's also been found that under realistic workloads, the
> driver is not only ~48x slower than ARMv8 CE, but due to massive driver
> overhead it actually consumes significantly *more* CPU cycles than doing
> the hashing directly on the CPU -- with much of that time spent in
> non-preemptible hardirq and softirq contexts
> (https://lore.kernel.org/linux-crypto/20260724020608.GA51735@sol/).  The
> proposed BAM locking fixes would only further degrade performance.
> 
> Additional bugs have been found as well
> (https://lore.kernel.org/linux-crypto/20260723205801.GD110634@quark/).
> Pending fixes for some bugs don't change the big picture.  Nor have
> security-related claims held up.  Of course, these issues are largely
> moot anyway when this driver's functionality isn't being used in
> practice, beyond the module loading due to it being in the kconfig.
> 
> Note that this removal does *not* imply that various other drivers in
> drivers/crypto/ don't have similar issues.  They do.  Rather, the
> evidence is just exceptionally clear for this one, in part because
> hardware availability has enabled independent testing.
> 
> Signed-off-by: Eric Biggers <ebiggers@kernel.org>

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>