> On 19. Aug 2026, at 23:56, Michael S. Tsirkin <[email protected]> wrote:
>
> On Wed, Aug 19, 2026 at 10:22:06AM +0100, Alex Bennée wrote:
>> We have outstanding guest exploitable bugs in the code which is fairly
>> complex and needs some serious love to clean it up. As off-CPU
>> cryptography acceleration seems to be waning in popularity lets just
>> deprecate the sub-system with a view to removing it in a couple of
>> cycles.
>>
>> Link: https://gitlab.com/qemu-project/qemu/-/work_items/3625
>> Signed-off-by: Alex Bennée <[email protected]>
>> Cc: Gonglei <[email protected]>
>
> Let's see what Gonglei thinks.
>
>> ---
>> docs/about/deprecated.rst | 14 ++++++++++++++
>> 1 file changed, 14 insertions(+)
>>
>> diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
>> index 0c656a968fc..3c22981fc8a 100644
>> --- a/docs/about/deprecated.rst
>> +++ b/docs/about/deprecated.rst
>> @@ -276,6 +276,20 @@ future release. Where no 'dh-params.pem' file is
>> provided, the DH
>> parameters will be automatically negotiated in accordance with
>> RFC7919.
>>
>> +Devices
>> +-------
>> +
>> +``virtio-crypto`` (since 11.2)
>> +''''''''''''''''''''''''''''''
>> +
>> +The ``virtio-crypto`` device emulation is quite complex code with a
>> +number of known flaws. It has never been migratable so is unlikely to
>> +be used in any serious virtualization setting. With most modern
>> +systems supporting on-CPU cryptography acceleration via their
>> +ISAs sets
>
> ISA sets?
Architecturally exposed instead of via PCIe/platform devices
>
>> the need for off-CPU acceleration is also reduced. Add to
>> +that the kernel has recently removed the ability to use off-CPU
>> +acceleration
>
> did it really? I thought it's just for af_alg?
The kernel’s own use cases - for disk encryption and co - aren’t
supported anymore using offloading - and AF_ALG is deprecated.
Drivers exposing a channel directly between hardware and the driver
(ConnectX NICs, Intel QAT for ex) remain, and userspace can
continue to use hardware crypto offloads through these or kTLS offload
which also remains.
For the former case though this means using a vendor-specific
library in userspace (qatlib for intel)
>
> and putting "recently" into cde will not age well.
>
>> suggests the time for this sort of off-load has passed.
>> +
>> Device options
>> --------------
>>
>>
>> --
>> 2.47.3
>
>
