On 22/7/26 13:57, Daniel P. Berrangé wrote:
Linux 7.1 has deprecated the AF_ALG crypto backend:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=a67afb1884ba815079bd43d5c998e155e03b08b6
And has documented it to be always slower than userspace crypto:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5624ea54f3ba5c83d2e5503411a31a8be0278c1e
as a result of dropping support for zero-copy and hardware
accelerators:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7524070f26d8d347c26787dc297fb844baa26abf
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ffdd2bc378953b525aca61902534e753f1f8e734
The main use case for the AF_ALG impl was to improve the performance
of virtio-crypto with the cryptodev-backend-builtin driver. In
practice this did not matter since 'cryptodev-backend-lkcf' can do
offload to the kernel via the keyctl syscall, and 'cryptodev-vhost-user'
can offload to an external process which can optionally integrate with
hardware accelerators without kernel assistance.
The AF_ALG backend has no user visible configuration options at runtime,
it is unconditionally tried with any use of the cipher APIs. So it does
not strictly have to go through the deprecation process, however, it is
left available initially in case there was an unexpected use case that
relies on it which may be faster with old kernels before the above Linux
commits.
Suggested-by: Thomas Huth <[email protected]>
Signed-off-by: Daniel P. Berrangé <[email protected]>
---
docs/about/deprecated.rst | 21 +++++++++++++++++++++
meson.build | 6 ++++++
2 files changed, 27 insertions(+)
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
