Hi Jens,
On 13/04/2023 08:14, Jens Wiklander wrote:
Adds a comments with a list of unsupported FF-A interfaces and
limitations in the implemented FF-A interfaces.
Signed-off-by: Jens Wiklander <jens.wiklan...@linaro.org>
---
xen/arch/arm/tee/ffa.c | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
index 0948cc636871..6424c222c885 100644
--- a/xen/arch/arm/tee/ffa.c
+++ b/xen/arch/arm/tee/ffa.c
@@ -13,6 +13,38 @@
* https://developer.arm.com/documentation/den0077/e
* TEEC-1.0C: TEE Client API Specification version 1.0c available at
*
https://globalplatform.org/specs-library/tee-client-api-specification/
+ *
+ * Notes on the the current implementstion.
+ *
+ * Unsupported FF-A interfaces:
+ * o FFA_MSG_POLL and FFA_MSG_SEND - deprecated in FF-A-1.1-REL0
+ * o FFA_MEM_RETRIEVE_* - Used when sharing memory from an SP to a VM
+ * o FFA_MEM_DONATE_* and FFA_MEM_LEND_* - Used when tranferring ownership
+ * or access of a memory readion
+ * o FFA_MSG_SEND2 and FFA_MSG_WAIT - Used for indirect messaging
+ * o FFA_MSG_YIELD
+ * o FFA_INTERRUPT - Used to report preemption
+ * o FFA_RUN
+ *
+ * Limitations in the implemented FF-A interfaces:
+ * o FFA_RXTX_MAP_*:
+ * - Maps at most 32 4k pages large RX and TX buffers
+ * - RT/TX buffers must be normal RAM
Can you explain why this is a problem?
+ * - Doesn't support forwarding this call on behalf of an endpoint
+ * o FFA_MEM_SHARE_*: only supports sharing
+ * - from a VM to an SP
+ * - with one borrower
+ * - with the memory transaction descriptor in the RX/TX buffer
+ * - normal memory
+ * - at most 512 kB large memory regions
+ * - at most 32 shared memory regions per guest
+ * o FFA_MSG_SEND_DIRECT_REQ:
+ * - only supported from a VM to an SP
+ *
+ * There are some large locked sections with ffa_tx_buffer_lock and
+ * ffa_rx_buffer_lock. Especially the ffa_tx_buffer_lock spinlock used
+ * around share_shm() is a very large locked section which can let one VM
+ * affect another VM.
*/
#include <xen/bitops.h>
Cheers,
--
Julien Grall
