[xen master] docs: add Arm FF-A mediator

[patchbot@xxxxxxx]

commit e6cb27f2f20d09dd2ba135fbc341a4dc98656e10
Author:     Jens Wiklander <jens.wiklander@xxxxxxxxxx>
AuthorDate: Mon Jul 31 14:15:36 2023 +0200
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Fri Aug 18 09:29:23 2023 +0100

    docs: add Arm FF-A mediator
    
    Describes a FF-A version 1.1 [1] mediator to communicate with a Secure
    Partition in secure world.
    
    [1] https://developer.arm.com/documentation/den0077/latest
    
    Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
    Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx>
    Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
    Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 CHANGELOG.md             |  2 ++
 SUPPORT.md               |  9 +++++++++
 docs/man/xl.cfg.5.pod.in | 15 +++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7e5efcabda..2a967f9f0e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,6 +24,8 @@ The format is based on [Keep a 
Changelog](https://keepachangelog.com/en/1.0.0/)
  - xl/libxl can customize SMBIOS strings for HVM guests.
  - Add support for AVX512-FP16 on x86.
  - On Arm, Xen supports guests running SVE/SVE2 instructions. (Tech Preview)
+ - On Arm, add suport for Firmware Framework for Arm A-profile (FF-A) Mediator
+   (Tech Preview)
 
 ### Removed
  - On x86, the "pku" command line option has been removed.  It has never
diff --git a/SUPPORT.md b/SUPPORT.md
index 1c9f0b7d8c..6ce0ec29b0 100644
--- a/SUPPORT.md
+++ b/SUPPORT.md
@@ -842,6 +842,15 @@ that covers the DMA of the device to be passed through.
 
 No support for QEMU backends in a 16K or 64K domain.
 
+### ARM: Firmware Framework for Arm A-profile (FF-A) Mediator
+
+    Status, Arm64: Tech Preview
+
+There are still some code paths where a vCPU may hog a pCPU longer than
+necessary. The FF-A mediator is not yet implemented for Arm32. Part of the
+FF-A specification is not supported, see the top comment in
+xen/arch/arm/tee/ffa.c for limitations.
+
 ### ARM: Guest Device Tree support
 
     Status: Supported
diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index a2bccd5b48..ec4864958e 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -1656,6 +1656,21 @@ in OP-TEE.
 
 This feature is a B<technology preview>.
 
+=item B<ffa>
+
+B<Arm only.> Allow a guest to communicate via FF-A with Secure Partitions
+(SP), default false.
+
+Currently only a small subset of the FF-A specification is supported. Just
+enough to communicate with OP-TEE. In general only direct messaging and
+sharing memory with one SP. More advanced use cases where memory might be
+shared or donated to multiple SPs are not supported.
+
+See L<https://developer.arm.com/documentation/den0077/latest> for more
+information about FF-A.
+
+This feature is a B<technology preview>.
+
 =back
 
 =back
--
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