docs: fusa: Define the requirements for XEN_VERSION hypercall.

Define the requirements which are common for all the commands.

Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@amd.com>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

docs/fusa/reqs/design-reqs/arm64/hypercall.rst

@@ -0,0 +1,60 @@
+.. SPDX-License-Identifier: CC-BY-4.0
+
+Hypercall
+=========
+
+Instruction
+-----------
+
+`XenSwdgn~arm64_hyp_instr~1`
+
+Description:
+Xen shall treat domain hvc instruction execution (with 0xEA1) as hypercall
+requests.
+
+Rationale:
+
+Comments:
+Hypercall is one of the communication mechanism between Xen and domains.
+Domains use hypercalls for various requests to Xen.
+The exception syndrome register should have the following values :-
+ESR_EL2.ISS should be 0xEA1.
+ESR_EL2.EC should be 0x16.
+
+Covers:
+ - `XenProd~version_hyp_first_param~1`
+ - `XenProd~version_hyp_second_param~1`
+
+Parameters
+----------
+
+`XenSwdgn~arm64_hyp_param~1`
+
+Description:
+Xen shall use x0 - x4 core registers to obtain the arguments for domain hypercall
+requests.
+
+Rationale:
+
+Comments:
+Xen shall read x0 for the first argument, x1 for the second argument and so on.
+
+Covers:
+ - `XenProd~version_hyp_first_param~1`
+ - `XenProd~version_hyp_second_param~1`
+
+Hypercall number
+----------------
+
+`XenSwdgn~arm64_hyp_num~1`
+
+Description:
+Xen shall read x16 to obtain the hypercall number.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenProd~version_hyp_first_param~1`
+ - `XenProd~version_hyp_second_param~1`

docs/fusa/reqs/index.rst

@@ -10,5 +10,7 @@ Requirements documentation
    market-reqs/reqs
    product-reqs/reqs
    product-reqs/arm64/reqs
+   product-reqs/version_hypercall
    design-reqs/arm64/generic-timer
    design-reqs/arm64/sbsa-uart
+   design-reqs/arm64/hypercall

docs/fusa/reqs/market-reqs/reqs.rst

@@ -79,3 +79,19 @@ Comments:
 
 Needs:
  - XenProd
+
+Version hypercall
+-----------------
+
+`XenMkt~version_hypercall~1`
+
+Description:
+Xen shall provide a hypercall for the domains to retrieve Xen's version, type
+and compilation information.
+
+Rationale:
+
+Comments:
+
+Needs:
+ - XenProd

docs/fusa/reqs/product-reqs/version_hypercall.rst

@@ -0,0 +1,42 @@
+.. SPDX-License-Identifier: CC-BY-4.0
+
+Version hypercall
+=================
+
+First Parameter
+---------------
+
+`XenProd~version_hyp_first_param~1`
+
+Description:
+Xen shall treat the value stored in x0 as the command number for the hypercall.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenMkt~version_hypercall~1`
+
+Needs:
+ - XenSwdgn
+
+Second Parameter
+----------------
+
+`XenProd~version_hyp_second_param~1`
+
+Description:
+Xen shall treat the value stored in x1 as a domain virtual address (mapped as
+Normal Inner Write-Back Outer Write-Back Inner-Shareable) to buffer in domain's
+memory.
+
+Rationale:
+
+Comments:
+
+Covers:
+ - `XenMkt~version_hypercall~1`
+
+Needs:
+ - XenSwdgn