docs: deprecate virtio-crypto
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 the deprecate the sub-system with a view to removing it in a couple of cycles. We can also remove the backend code at that point as well. Link: https://gitlab.com/qemu-project/qemu/-/work_items/3625 Reviewed-by: Mohamed Mediouni <mohamed@unpredictable.fr> Reviewed-by: Thomas Huth <thuth@redhat.com> Message-ID: <20260824-fixes-for-11-2-v2-7-352c6b890402@linaro.org> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Alex Bennée committed
Aug 24, 2026 at 16:24 UTC
aaf25b4ccc45dd96d8ffe4e7e41bf3956c345507
1 file changed
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docs/about/deprecated.rst
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@@ -276,6 +276,24 @@ future release. Where no 'dh-params.pem' file is provided, the DH
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parameters will be automatically negotiated in accordance with
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RFC7919.
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+Devices
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+-------
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+
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+``virtio-crypto`` and cryptodev backends (since 11.2)
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+'''''''''''''''''''''''''''''''''''''''''''''''''''''
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+
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+The ``virtio-crypto`` device emulation is quite complex code with a
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+number of known flaws. It has never been migratable, so it is
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+unlikely to be used in any serious virtualization setting. Modern
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+ISAs provide on-CPU cryptography instructions (e.g. AES-NI/VAES,
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+armv8 crypto extensions), and the Linux kernel deprecated AF_ALG
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+and dropped its off-CPU accelerator support in Linux 7.2, removing
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+the primary userspace path for off-CPU crypto acceleration. The
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+time for this sort of off-load has passed.
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+
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+As this is the only device that uses the cryptodev backends these will
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+be removed at the same time the ``virtio-crypto`` device is.
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+
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Device options
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--------------
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