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According to the FF-A spec (Buffer states and ownership), after a producer has written into a buffer, it is "full" and now owned by the consumer. The producer won't be able to use that buffer, until the consumer hands it over with an invocation such as RX_RELEASE. It is clear in the following paragraph (Transfer of buffer ownership), that MEM_RETRIEVE_RESP is transferring the ownership from producer (in our case SPM) to consumer (hypervisor). RX_RELEASE is therefore mandatory here. It is less clear though what is happening with MEM_FRAG_TX. But this invocation, as a response to MEM_FRAG_RX writes into the same hypervisor RX buffer (see paragraph "Transmission of transaction descriptor in fragments"). Also this is matching the TF-A implementation where the RX buffer is marked "full" during a MEM_FRAG_RX. Release the RX hypervisor buffer in those two cases. This will unblock later invocations using this buffer which would otherwise fail. (RETRIEVE_REQ, MEM_FRAG_RX and PARTITION_INFO_GET). Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com> Link: https://lore.kernel.org/r/20240611175317.1220842-1-vdonnefort@google.com Signed-off-by: Marc Zyngier <maz@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.